TECHNICAL REPORT DOCUMENTATION PAGE 1. Report No, 2, Government Accession No, 3. Recipient's Catalog No,

TX -99/7-4936-1

4, Title and Subtitle 5, Report Date Development of Guidelines for Control of Radio-Frequency March,2001 Interference in Vehicles -- Phase II: Final Report

6. Performing Organization Code TechMRT

7. Author(s) 8. Performing Organization Report Ibomas Trost No. 4936-1

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) Texas Tech University Center for Multidisciplinary Research in Transportation

Box 41023 11. Contract or Grant No. Lubbock, Texas 79409-1023 Project 7-4936

12. Sponsoring Agency Name and Address 13. Type of Report and Period Cover Texas Department of Transportation Final Report Research and Technology

P. O. Box 5080 14. Sponsoring Agency Code Austin, TX 78763-5080

15. Supplementary Notes Study conducted in cooperation with the Texas Department of Transportation. Research Project Title: "Development of Guidelines for Control of Radio-Frequency Interference in

Vehicles-Phase II"

16. Abstract

This report describes the second and final phase of a study of vehicle-generated radio interference in Texas Department of Transportation vehicles. The results of the first phase are contained in a 1998 report. The emphasis throughout the study has been on the test methods used to characterize the interference. The second phase took place over the 16-month period from May 1, 1999 to August 31, 2000. Ibree faculty members and three students carried out the research at Texas Tech University. The Main results of the study were the formulation of an expanded version of the TxDOT Tex-899-B test, worked out in cooperation with the vehicle manufacturers, and the determination that other versions are possible, but while more precise, suffer the drawback of added complexity.

17. Key Words 18. Distribution Statement radio interference, noise interference, vehicle No restrictions. This document is available to the

generated interference public through the National Technical Information Service, Springfield, Virginia 22161

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price

Unclassified Unclassified 198

Form DOT F 1700.7 (8-72)

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Development of Guidelines for Control of Radio-Frequency Interference in Vehicles -

Phase II: Final Report

by

Thomas F. Trost Department of Electrical Engineering

Texas Tech University Lubbock, Texas

Research Report Number 7-4936

conducted for

Texas Department of Transportation

by the

CENTER FOR MUL TICISIPLINARY RESEARCH IN TRANSPORTATION

TEXAS TECH UNIVERSITY

March 2001

III

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IMPLEMENTATION STATEMENT

Included among the results of the present study is a newly expanded version of the TxDOT Tex-899-B radio-interference test. This version includes several improvements to the original, which serve to make a good test even better. It is recommended that a test document based on this expanded version be included in TxDOT procurement specifications for new motor vehicles.

Time will be required to judge the effectiveness of the expanded test in reducing the incidence of interference problems in new vehicles. At some point, consultation with the vehicle manufacturers to discuss the progress in this regard would seem advisable.

The survey indicates that some other states suffer radio-interference problems similar to those of TxDOT. The test document mentioned above should be sent to these states, so they can benefit from TxDOT's experience. It may also be a good idea to arrange some type of forum with these states, e.g. a special session at a national meeting, to facilitate continued exchange of information on vehicle-generated radio interference.

v

Prepared in cooperation with the Texas Department of Transportation and the U.S. Department of Transportation, Federal Highway Administration.

VI

AUTHOR'S DISCLAIMER

The contents of this report reflect the views of the authors who are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official view of policies of the Department of Transportation or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation.

PATENT DISCLAIMER

There was no invention or discovery conceived or first actually reduced to practice in the course of or under this contract, including any art, method, process, machine, manufacture, design or composition of matter, or any new useful improvement thereof, or any variety of plant which is or may be patentable under the patent laws of the United States of America or any foreign country.

ENGINEERING DISCLAIMER

Not intended for construction, bidding, or permit purposes.

TRADE NAMES AND MANUFACTURERS' NAMES

The United States Government and the State of Texas do not endorse products or manufacturers. Trade or manufacturers' names appear herein solely because they are considered essential to the object of this report.

vu

Symbol When You Know Multiply By To Find Symbol Symbol When You Know Multiply By To Find Symbol

LENGTH LENGTH in inches 25.4 millimeters mm mm millimeters 0.039 inches in It feet 0.305 meters m m meters 3.28 feet It yd yards 0.914 meters m m meters 1.09 yards yd mi miles 1.81 kilometers km km kilo meters 0.621 miles mi

AREA AREA

in' square inches 645.2 square millimeters mm' mm' square millimeters 0.00 18 square inches int f't2 square feet 0.093 square meters m' m' square melers 10.764 square feet ft2 yet'- square yards 0.836 square meters m' mt square melers 1.195 square yards ycP ac aaes 0.405 hectate$ ha ha hectares 2.47 acres ac mi' square miles 2.59 square kilomelers km' km' square kilometers 0.388 square miles mi'

VOLUME VOLUME

11 0% lIuidounces 29.57 milliliters mL mL milliliters 0.034 fluid ounces fl OZ

III gal gallOO$ 3.785 Uters L L liters 0.264 gallons gal ft2 cubic feet 0.028 cubic meters m3 m3 cubic meters 35.71 cubic feel ftl y6' cubic yards 0.765 cubic meters m3 m3 cubic melers 1.307 cubic yards ycP

NOTE: Volumes greater than 1000 I shall be shown in ml.

MASS MASS

oz ounces 28.35 grams g g grams 0.035 ounces oz Ib pounds 0.454 kilograms kg kg kilograms 2.202 pounds Ib T short tons (2000 Ib) 0.907 megagrams Mg Mg megagrams 1.103 short tons (2000 Ib) T

(or 'metric ton') (or't') (or'I') (or 'metric ton")

TEMPERATURE (exJct) TEMPERATURE (exact)

OF Fahrenheit 5(F-32)19 Celcius °C °C Celcius 1.BC + 32 Fahrenheit OF temperature or (F-32)11.8 lemperature temperature temperature

ILLUMINATION ILLUMINATION

fe foot-candles 10.76 lu)( Ix Ix lux 0.0929 foot-candles Ic fl loot·Lamberts 3.426 candela/m' cdlm' cdlm' candela/m' 0.2919 foot-Lamberts H

FORCE and PRESSURE or STRESS FORCE and PRESSURE or STRESS

Ibf poundforce 4.45 newtons N N newtons 0.225 poundlorea Ibf Ibflinl poundforoe per 6.B9 kilopascals kPa kPa kilopascals 0.145 poundlorce per Ibflln'

square inch square inch

• SI is t~e sy~bollor the I~temation~ System o~ Units .. ~~"':?P~~t.e (Revised September 1993)

ACKNOWLEDGMENT

The TxDOT Project Director for this project was Don Lewis, Fleet Manager, General Services Division, Austin, Texas.

Research performed in cooperation with the Texas Department of Transportation.

IX

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TABLE OF CONTENTS

Technical Documentation Page ............................................................................................... . Title Page.................................................................................................................................. III

Implementation Statement .............. .... ......... .... ................... ...... .................................... ........... v Disclaimers............................................................................................................................... VB

Metric Table ............................................................................................................................. Vlll

Acknowledgment .... ... .............................................................................................................. IX

Table of Contents ..... ............................. ................................................................................... XI

List of Tables............................................................................................................................ Xlll

List of Figures .......................................................................................................................... XIV

ABSTRACT ........................................................................................................................... .

I. INTRODUCTION A. Motivation ..................................................................................................................... 2 B. Definition of Noise ........................................................................................................ 2 C. Project Personnel ........................................................................................................... 2 D. Equipment Support........................................................................................................ 3 E. TxDOT Staff Support ................. ................................................................................... 3 F. Interaction with the TEAM ............................................................................................ 3 G. Pulsed Electric Currents ................................................................................................ 3 H. Vehicle EMC Tests........................................................................................................ 4 I. Project Objective and Method ...................................................................................... 4 J. Typical Testing Sequence ............................................................................................. 5

11. LABORATORY EXPERIMENTS A. Simulation of Multiple Noise Sources......................................................................... 7 B. Characterization of Noise Blankers ............................................................................. 9 C. Comparison of Average Detectors

1. Average or peak? ................................................................. ................................... 11 2. Laboratory measurements....................................................................................... 12 3. Video averaging...................................................................................................... 15

Ill. WHOLE-VEIDCLE TESTS A. Vehicles, Instrumentation, and Site ............................................................................. 16 B. Noise from DC Motors ....................... ......................................................................... 19 C. Noise from Electronic Modules ................................................................................... 20 D. Vehicle Pass/Fail Results............................................................................................. 22 E. Antenna Comparison.................... ........... ......... ........... ...... ......... ......... ............ ...... ....... 26 F. Questions

1. Current on outside of antenna cable ........ .............. ....................................... .......... 27 2. Surface below the vehicle ....................................................................................... 27 3. Vehicle electromagnetic resonances....................................................................... 27

G. Diesel Truck................................................................................................................. 28 H. Limit on Electric Field Strength ........................................... ...... ............... ........... ....... 28

Xl

IV. SURVEY OF STATE DEPARTMENTS OF TRANSPORTATION

V. CONCLUSIONS A. A Pattern for Peak and Average Limits.... .......... .................... ...... .... ....... ..... ....... ..... ... 31 B. Options for Testing New Vehicles for TxDOT Service ............................................... 33 C. Expanded Tex-899-B Test............................................................................................ 34 D. Future Directions.......................................................................................................... 35

REFERENCES. ........................ .............................................................................................. 36

APPENDICES A. Expanded Tex-899-B Test B. MSEE Thesis by Jongsin Yun C. IEEE Symposium Paper D. MSEE Thesis by Prasanna Bahukudumbi

Survey of State DOTs

Xll

Table I Table 2 Table 3 Table 4 Table 5 Table 6 Table 7 Table S Table 9 Table 10

LIST OF TABLES

Modified J551/4 RF-emissions test for new TxDOT vehicles Noise Blankers in TxDOT radios: general data Laboratory test of noise blanker performance of TxDOT radios: part I Laboratory test of noise blanker performance of TxDOT radios: part II List of trucks tested at TTU during 2000 Typical baseline noise levels (47.IS MHz) Spurious emissions from instrumentation Electronic-module emissions (46.9 MHz to 47.S MHz) Return-loss data for three antennas Tex-S99-B results for three antennas

Xlll

9 9 10 10 16 17 19 20 26 27

Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Figure 8

Figure 9 Figure 10 Figure 11 Figure 12

LIST OF FIGURES

EMC testing of new TxDOT vehicles Block diagram of bench-top test system Laboratory evaluation ofRF noise with EMI receiver and FM radio Averaging with 9 kHz bandwidth Averaging with 120 kHz bandwidth Texas Tech graduate students setting up for the testing of a TxDOT truck Rolling EMI Measurement System Used for SAE J551/4 and TxDOT Tex-899-B Testing Oscillograph showing example of module noise from 1999 Dodge RAM 2500 pickup truck Spectrum of peak module noise from Dodge truck Peak and average module noise from Dodge truck Peak and average module noise compared to SINAD measurement Trajectories of peak and average limits

XIV

6 7 8

13 14 17 18

21

23 24 25 32

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1. INTRODUCTION

" ... an important part of that fundamental problem of producing a desired effect is simultaneously preventing undesired effects"- Ronold W.P. King, Transmission Lines, Antennas, and Wave Guides, 1945

A. Motivation The Texas Department of Transportation (TxDOT) sometimes finds that radio

interference or noise is generated by the electrical system of a new fleet vehicle at such a level that it degrades the performance of the receiver in the two-way FM radio carried in the vehicle. The problem has persisted, in varying degree, over a period of years. In response, TxDOT has developed a test method to identify offending vehicles before they are put into service. And a procedure has been adopted whereby offending vehicles are modified so that they will pass the test and thus may enter the fleet.

In an effort to move away from this cumbersome test-and-fix activity, TxDOT initiated the present research project as an independent investigation of the problem, focusing on testing methodologies and on cooperation with the vehicle manufacturers. The first phase of the project was completed in 1998 [1], and the second and final phase is now also complete.

B. Definition of Noise The term "noise" (or interference) as used throughout this report refers to any

electromagnetic disturbance which is picked up by a TxDOT radio and, if strong enough, can interfere with the reception of signals by the radio. The sound of this "noise" in the radio speaker can take the form of random clicks or pops, a tone, distortion of the desired signal, or a quieting of the desired signaL

C. Project Personnel The following faculty members and students conducted the Phase IT research; they were

all members of the Department of Electrical Engineering at Texas Tech University (TTU). Faculty members:

Thomas F. Trost, Principal Investigator David J. Mehrl Thomas F. Krile

Graduate students: Prasanna Bahukudumbi (MSEE degree, 2000) Jongsin Yun (MSEE degree, 2000)

Undergraduate student: Chad Bonner (BSEE degree, 2000)

2

D. Equipment Support Our pnmary mstrument for the measurement of radio-frequency (RF) noise, a Rohde &

Schwarz ESVP receiver, was loaned to us from the electromagnetic compatibility (EMC) laboratory at Dell Computer Corp. by David Staggs. Other instrumentation was supplied by the TTU Department of Electrical Engineering or was rented.

Jackie Anderson of the TxDOT Ft. Worth office kindly supplied two Dodge trucks for radio-frequency interference (RFI) testing.

Lucinda Martin of the Texas Tech University motor pool kindly supplied a Chevrolet, a Dodge, and a Ford truck for RFI testing.

E. TxDOT Staff Support Informatlon on the history of TxDOT radio-frequency interference problems and good

suggestions for the current project were supplied by members of the TxDOT radio engineering staff, Leonard Bryan (Lubbock), Richard Herndon, Robert Packert, and Pat Warsham (Austin), and by Curtis Reinert and Don Lewis of the Purchasing and Equipment Sections (GSA, Austin).

Bradford Rehm of Professional Testing, Inc., in Round Rock, who is under contract to TxDOT for RFI testing, was also very helpful.

F. Interaction with the TEAM Durmg the course of the project, Principal Investigator Thomas Trost together with

Project Director and TxDOT Fleet Manager Don Lewis delivered periodic briefings to the SAE Electromagnetic Radiation (EMR) Committee in Detroit. The members of this committee were the TEAM- the Technical Expert Advisory Members for the project; and they provided many good comments and suggestions during the briefings. Among the TEAM were EMC engineers from DaimlerChrysler, Ford, and General Motors, all major suppliers of TxDOT vehicles; and thus the briefings also provided an opportunity for discussions between Mr. Lewis and his suppliers regarding specific concerns on the subject of vehicle radio interference. These engineers were Poul Andersen ofDaimlerChrysler, Keith Frazier and Richard Kautz from Ford, and Donald Seyerle from General Motors.

The dates of the briefings were March 5, 1999, September 10, 1999, January 14, 2000, and January 19,2001. Prof. Trost also held discussions with several of the TEAM individually while attending the international IEEE (Institute of Electrical and Electronics Engineers) EMC meeting in Washington, D.C., on August 21-25, 2000.

G. Pulsed Electric Currents III the early days of radio the first transmitters used spark gaps to generate their radio­

frequency signals. Thus we should not be surprised to find that any sparking device in use nowadays is a potential source of radio noise or interference to nearby electronic equipment.

More generally, not only sparks but any pulsed electric current can be a noise source because of its inherent broad frequency spectrum. In order to understand the basic nature of this spectrum, we can mathematically model the waveform of a current pulse as trapezoidal. We then find from Fourier analysis that the envelope ofthe spectrum first falls off slowly, as f-l or 20 dB per decade, with increasing frequency and then more rapidly, as f-2 or 40 dB per decade.

3

The frequency at which the transition between slopes occurs is approximately equal to 1I(n8), where 8 is the risetime of the trapezoid [2]. Thus if the risetime were 5 ns, the transition frequency would be 64 MHz. If the current pulse repeats in time at a slow rate, then there are many closely spaced frequency components under the envelope. If the pulse repeats rapidly, then there are just a few widely spaced components under the envelope.

Nearly all the electromagnetic noise sources found in a motor vehicle are the result of pulsed electric currents. There are the sparks at the electrodes of the spark plugs and the sparks occurring on the commutators of the DC motors that run the HV AC fan, fuel pump, etc. The vehicle's electronic modules also produce noise from pulses because the clocks in the microcontrollers generate pulsed signals and all the digital information is pulsed. In addition, pulse-width-modulated DC power is used to drive some motors, actuators, and injectors.

The transition-frequency value of 64 MHz stated above is a realistic one for motor­vehicle sources. Since the primary TxDOT communication band is located at 47 MHz, it lies within the slowly falling portion of the noise spectrum, where the noise may still be strong enough to cause significant interference in the TxDOT radio receivers. Thus on the basis of this simple mathematical model we are alerted to a potential problem. Of course, good design of vehicle systems can mitigate noise radiation. For readers who may be interested, some design handbooks are listed in the references [3,4,5].

H. Vehicle EMC Tests The branch of electrical engineering which deals with problems of interference between

electrical devices, like that addressed in the present project, is known as electromagnetic compatibility (EMC); and numerous EMC test and certification procedures have been developed over the years.

Two EMC test standards were of primary interest in this project, the TxDOT test referred to above in Section A, Tex-899-B [6], and a Society of Automotive Engineers test, SAE J55114 [7]. Both of these tests are concerned with placing limits on the radio-frequency (RP) noise emissions of a motor vehicle, but they are fundamentally different in nature. J55114 involves the measurement of RP emissions received by an antenna on the vehicle. Tex-899-B involves the measurement of the effect on the audio-frequency (AF) output of a radio in the vehicle from the emissions received by the antenna, when a signal is also present. J55114 is an RP noise amplitude test, and Tex-899-B is an AF SINAD test (measuring the AF signal-to-noise-and­distortion ratio) [8].

The Tex-899-B test in fact contains two parts. One of them deals with vehicle RP emissions, as discussed above, and was the one of primary interest to us; it is referred to as the "egress" test [6]. The other part, the so-called "ingress" test, deals with the susceptibility of the various vehicle systems to upset from radiation from the TxDOT radio transmitter. In this report, as we refer to Tex-899-B, unless otherwise noted, we will mean just the egress part.

I. Project Objective and Method Tex-899-B is a specialized test well suited to uncovering potential TxDOT interference

problems because it employs a radio like that used in the TxDOT fleet. In contrast, J55114 is a more general industry standard, and, as we learned in Phase I, 155114 is not useful, as it stands, for testing vehicles for TxOOT service.

4

Our objective in Phase IT was to detennine whether some modified fonn of the J55114 test could be found that would be as effective as Tex-899-B and that the automakers would be willing to perfonn to qualify their vehicles for TxDOT service. J55114 seemed like a better candidate than Tex-899-B for use by the automakers primarily because it appeared to be less time-consuming to carry out.

The range of frequencies in which most TxDOT radios operate, and where the noise problem exists, lies in the two-way radio low-band VHF range and extends from 47.02 MHz to 47.34 MHz. This is the range the project concentrated on.

Our approach in Phase IT had several components. First, we perfonned bench-top tests related to J55114 and Tex-899-B using TxDOT radios. The testing was done in a laboratory at ITV. Second, we wrote a computer program to provide a theoretical baseline for the laboratory tests. Third, we perfonned outdoor whole-vehicle tests on TxDOT trucks. This testing was done at a low-noise location several miles outside of Lubbock, and five trucks were tested. Fourth, we conducted a survey of other state DOTs around the country. And finally, we applied all of the information gained to arrive at a number of conclusions and to propose a new version of Tex-899-B in which the option of using a modified fonn of J55114 is included [Appendix A].

J. Typical Testing Sequence Figure 1 shows a flow chart that graphically illustrates several of the ideas discussed in

the sections above. The chart traces the progress of a new motor vehicle through the steps of testing by the automaker, delivery by a dealer to TxDOT, and testing for TxDOT by Professional Testing, Inc. The box labeled INPUr FROM TillS PROJECT shows the main point of application of our research results. The hope is that our new version of the Tex-899-B test will provide the automakers with a valuable tool to help them develop vehicles suitable for TxDOT service, thus obviating the need for the path labeled BACK TO DEALER.

5

I

I

I /

/ ____ ,L _______ , I ,---------, / I

~--~~~--~ I I : NEW VEHICLE

I 1----10.101 TESTING Pass I

~ (SAE J551/4 or other)

I I I L-_____ ----I

Fail I I I I I I I I I I I I I

'-- MODIFYING 14~----'

AUTOMAKER L __________ _

r

DEALER

~---- -------------------------------------I ~, I I I I I I TAKE BACK TO DEALER ?! I l DELIVERY ~: I I I 1r I I I I I I SEND TO TESTING Fail/I I 10. I I PRO. TEST. ,.. (TEX-899-8) I

I Pass.. FLEET I I ... I I I I I

: TXDOT : L ____________________________________ 1

Figure 1. EMC testing of new TxDOT vehicles

6

II. LABORATORY EXPERIMENTS

A. Simulation of Multiple Noise Sources Our main laboratory activities during Phase IT were the simulation of mUltiple noise

sources, the characterization of the noise blanker circuits in TxDOT radios, and a performance comparison of the average detectors in our EMI (electromagnetic interference) receiver and spectrum analyzer.

In Phase I of the project, motor-vehicle noise sources were simulated one at a time in our laboratory [9]. A block diagram of our laboratory apparatus is shown if Figure 2 and a photograph in Figure 3. A J551/4 type of measurement was obtained with the EMI receiver, which was set for peak detection; and a Tex-899-B measurement was made with the FM radio, FM signal generator, and SINAD meter.

NOISE SOURCES

• • •

FM SIGNAL GENERATOR

HYBRID JUNCTION

EMI RECEIVER

Figure 2. Block diagram of bench-top test system

7

SINAD METER

Figure 3. Laboratory evaluation of RP noise with EMI receiver and FM radio

In Phase IT the apparatus was similar, but we operated two or three of the noise sources simultaneously. Our results are detailed in the Master's thesis by J. Yun [Appendix B], and they are summarized in a paper written by Prof. Trost in February 2000 and presented at the 2000 International IEEE EMC Symposium [Appendix C]. The primary conclusion of the symposium paper is that a degree of correlation can be achieved between the TxDOT Tex-899-B test and the SAE J551/4 test if certain changes are made in the J55114 limits. For the convenience of the reader, a copy of the table from the paper containing the new limits is reproduced here as Table 1. The abbreviation BW stands for bandwidth, and NB stands for narrow-band « 15 kHz).

This table represented our best estimate of a suitable J55114 type of test as of early 2000. Subsequently, during the spring and summer of 2000, we conducted additional laboratory tests and whole-vehicle tests on five vehicles. We gained further insight into J55114 testing, especially in regard to the use of average rather than peak detection and in regard to the characteristics of electronic-module noise. However the procedure in Table 1 continues to represent a suitable test, if one change is made: the removal of the restriction NB on the module noise, so that all module noise is included.

The additional laboratory tests in 2000 were carried out by P. Bahukudumbi [Appendix D]. He used the setup in Figure 2 to study DC-motor noise, employing the Rohde & Schwarz ESVP with average detection as the EMI receiver. He determined that the Tex-899-B limit corresponds to a J551/4 average limit of3 dBIlV, and he suggested that this limit could be used rather than the J55114 peak limit of 40 dB).! V shown in Table 1. This possibility is further discussed in Chapter rn, Section B.

8

No limit is stated in Table 1 for the spark-ignition noise that exists when a vehicle engine is running. This noise can achieve high peak values. However in our laboratory simulations of this noise, the noise blanker circuits in the TxDOT radios very effectively eliminated it even when it was adjusted to be much stronger than on the vehicles. It is not thought to be a threat.

Table 1. Modified J551/4 RF-emissions test for new TxDOT vehicles

Test Measurement Limit Comment Configurati on BW (kHz) (dBJlV)

1. Run engine until warm 2. All OFF 9 -9 Ambient 3. All OFF 120 34 Ambient 4. Engine OFF, key ON 9 -3 NB electronic-

module emissions 5. Engine OFF, key ON, 120 40 DC-motor emissions

DC motors ON

B. Characterization of Noise Blankers The noise blankers, or extenders as they are sometimes called, in the TxDOT FM radios

perform the extremely valuable function of removing spark-ignition noise and reducing DC­motor noise from the radio output. The blankers in the two primary TxDOT radios, the MaraTrac and the RANGRTM, perform somewhat differently; and a number of their characteristics are given in Tables 2, 3, and 4.

Table 2. Noise blankers in TxDOT radios: general data

Blanker Characteristic

Type of circuit

Blanking disable/enable

Motorola MaraTrac

IF detect and IF blank

Push button

9

Radio General Electric RANGRTM

IF detect and IF blank

Internal jumpers

Table 3. Laboratory test of noise blanker performance of TxDOT radios: part I

Pulse length of noise pulses = 10 ns Various pulse rates and amplitudes

Blanker Characteristic

Length of blanking pulses

Minimum amplitude of noise pulses for blanking

Maximum amplitude of noise pulses for blanking

Pulse-rate shut down

MaraTrac

8 J..ls

3mV

>7V

300 kpps

Radio RANGRTM

2 J..ls

2mV

>7V

250 kpps

Table 4. Laboratory test of noise blanker performance of TxDOT radios: part II

Pulse rate of noise pulses = 1500 pps Various pulse lengths and carrier frequencies

Type of Noise Pulse Radio

Short (50 ns) DC

Long (50 J..ls) DC

Short (50 ns) RF

Long (50 J..ls) RF

Ma ra Trac

Blanked

Blanked

Blanked

Blanked

10

RANGRTM

Blanked

Blanked

Blanked

Not blanked

The characteristics listed in Table 3 show the two radios to perfonn about the same except that the MaraTrac has longer blanking pulses. This gives the MaraTrac increased blanking capability.

The noise pulses labeled "DC" in Table 4 are approximately rectangular voltage pulses. The pulses labeled "RP' are approximately rectangular AM voltage pulses with a carrier frequency set equal to the frequency to which the radios are tuned, typically 47.18 MHz. Our laboratory testing has revealed the following infonnation: For the short DC, long DC, and short RF pulses, both radios provide effective blanking. However the radios respond differently to the long RF pulses.

The short DC and short RF noise pulses are successfully blanked because they are shorter than the length of the radio blanking pulses. For the long DC pulses, the low-frequency cutoff characteristic of the radios removes the middle portion of the pulses, converting each long pulse into two short ones, which are then readily blanked.

For the case of the long RF noise pulses, the MaraTrac' s blanking pulse increases in length to match the noise pulse while the RANGRTM's blanking pulse remains short. Thus the MaraTrac blanks the long RF pulses while the RANGRTM does not. This gives the MaraTrac some advantage in blanking.

In addition to the noise-blanker testing described above, we also carried out the test procedure used by TxDOT in the acceptance testing of new radios [10]. This procedure involves using an HP 222A pulse generator to provide 100 ns 10kHz pulses. We verified that the MaraTrac and RANGR ™ radios both passed this test. Also of interest in regard to noise-blanker testing is the relevant section in TlNEIA-603 [11].

C. Comparison of Average Detectors 1. Average or peak?

In considering the use of a test like J55114 for TxDOT vehicles, the idea of employing average rather than peak detection seems worth exploring. The appeal of average detection stems from the fact that the noise blanker in a TxDOT radio removes the sharp peaks in the noise, and therefore to get a result from a J55114 test that correlates well with the response of the radio, peak detection would seem much less desirable than average (or perhaps RMS) detection. Here are some of the pros and cons of average detection.

Advantages of measuring average rather than peak values: (1) Can uncover narrow-band emissions in presence of broad-band noise (ii) Allows testing various vehicle noise sources with engine running by suppressing

spark-ignition pulses (iii) Can be expected to give better correlation with Tex-899-B for impulsive noise

sources because it acts somewhat like the noise blanker in a TxDOT radio (iv) Can supply insight into noise mechanisms when used together with peak

measurements Disadvantages of measuring average rather than peak values: (i) Some spectrum analyzers do not measure average values (ii) EMI receivers may not have enough dynamic range to measure average values of

some noise sources (iii) The limits of accuracy of average detectors may not be well established in the EMC

community

11

Based on the advantages listed above, we investigated average detection in the laboratory and employed it in our vehicle tests. From our results we determined average-detection limits on vehicle noise emissions. No such limits exist in SAE J55114; only peak and quasi-peak are given. Our laboratory work is discussed in the next section, and the vehicle tests are described in Chapter ill. 2. Laboratory measurements

In the laboratory we characterized the average detectors in two instruments, an R&S ESVP receiver and a Hewlett-Packard E7401A EMC analyzer. The HP analyzer is a spectrum analyzer with some additional features, including a built-in low-noise preamplifier and an average detector.

Figures 4 and 5 show our results for the two instruments. The figures are duplicates of those contained in the Master's thesis of P. Bahukudumbi [Appendix D]. The noise source connected to the instruments was a pulse generator adjusted to give varying repetition rate and constant amplitude and pulse length. Plotted out in the figures is the measured peak-to-average ratio (sometimes called the crest factor) versus the repetition rate for each of the two bandwidths of interest, 9 kHz and 120 kHz. Curves are shown for various instrument conditions as indicated in the legend. Prof. Krile wrote a MA1LAB program to numerically simulate the response of the average detector in the R&S ESVP receiver if it were ideal, and his theoretical curve is shown in the figures along with those measured. It is essentially a straight line with a slope of minus 20 dB per decade. (See Appendix D for details of the MA TLAB program.)

In Figure 4 the ESVP receiver bandwidth is given as 9 kHz. In fact the specification sheet for the receiver lists the bandwidth as 10 kHz. We carried out careful measurements of the shape ofthe passband and compared the results to the official CISPR 9 kHz spectral mask [12], and we found that the passband does indeed qualify as 9 kHz. Thus, in the present report we use the values 9 kHz and 10kHz interchangeably.

Besides using peak and average detection, we also experimented with the use of quasi­peak detection, but could find no benefit from it in the TxDOT situation.

12

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13

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14

The main conclusions to be drawn from Figures 4 and 5 are that the average detectors in the two instruments behave somewhat differently and that there can be significant deviations from ideal (theoretical) performance especially at large values of peak-to-average ratio. Some details are given by P. Bahukudumbi [Appendix D].

3. Video averaging Our HP EMC analyzer has a "video averaging" function, which is not exactly an average

detector but which was used for one of the curves in Figures 4 and 5. Many spectrum analyzers have this feature, in which the values displayed on the screen, either dB values or amplitudes, are averaged together at each frequency. Using the dB values amounts to adding together the logarithms of the amplitudes, which corresponds to multiplying the amplitudes themselves; and the result is the calculation of their geometric mean. It is well known to mathematicians that the geometric mean of a collection of positive numbers is always less than or equal to the arithmetic mean. A proof is contained, for example, in the book by W. Rudin [13].

This result is one reason why using video averaging can yield a different result than using an average detector. And there is another possible reason for a difference. Video averaging uses samples of the signal which are separated by the analyzer sweep time, not a continuous record of the signal. So short-duration features in the signal, impulses for example, could be missed.

15

Ill. WHOLE-VEHICLE TESTS

A. Vehicles, Instrumentation, and Site Our main vehicle-testing activity involved conducting Tex-899-B and J55114 tests on five

pickup trucks: we searched for DC-motor noise and electronic-module noise; we compared the pass-fail results of the two tests; and we tried out the use of average detection in J55114. Other activities included carrying out a comparison of three different antennas on one of the trucks and assessing the noise emissions from our measurement equipment.

A list of the trucks that were tested in Phase IT is given in Table 5. The TxDOT trucks had been converted to run on propane as well as gasoline, the Texas Tech University trucks had not. Testing was conducted from April 2000 through August 2000.

Table 5. List of trucks tested at TTU during 2000

Make Model Year VIN Fuel Equipment Owner

Dodge RAM1500 1999 1B 7HC 16Y6XS309435 Gas/ ABS, airbag TxDOT V8 (TxDOT 2-5643-G) Prop

Dodge RAM1500 1999 1B7HC16Y5XS309443 Gas! ABS, airbag TxDOT V8 (TxDOT 2-5649-G) Prop

Dodge RAM25 00 1999 3B6KC26Z5XM59 1021 Gas ABS, airbag TTU V8 (Tx768429)

Ford F250 1998 IFTPF27L4VVKB76975 Gas ABS, airbag TTU V8 (Tx742655)

Chevrolet SlO 1999 IGCCS14X8X8195815 Gas ABS, airbag TTU V6 (Tx763730)

Figure 6 shows one of the vehicles at our rural test site with students preparing for a test. The cart and the instrumentation it carried are shown in Figure 7. All the instrumentation was powered by the two 12-V batteries. J55114 measurements were done with the R&S ESVP receiver. Tex-899-B measurements were done with the TxDOT (MaraTrac) radio, using the R&S CMS54 Radiocommunication Service Monitor as both an FM signal generator and a SINAD meter. The notation MM antenna refers to our magnetic-mounted Larsen NMO-50 base­loaded whip antenna. The Fluke 99B oscilloscope was used to examine video waveforms from the ESVP receiver. The HP E7401A analyzer mentioned above in Chapter IT was used only to get a quick display of the noise levels across a range of frequencies, and it is not shown in Figure 7.

16

Figure 6. Texas Tech graduate students setting up for the testing of a TxDOT truck

The lower limit of our measurement capability is always set by instrumentation and ambient noise. In Table 6 we show the internal noise level of the ESVP receiver and the ambient noise level at our test site. For the TxDOT MaraTrac radio, the 12 dB SINAD test gave a value of -12 dBI..IV for radio sensitivity and - 8 to - 10 dBflV for ambient.

Table 6. Typical baseline noise levels (47.18 MHz)

Pk (dBIlV) Avg (dBIlV) 9kHz 120kHz 9kHz 120 kHz

ESVP -12 1 -23 -13 Receiver

Outdoor -9 5 -20 -9 Ambient

17

R&S ESVP receiver

MM antenna

R&S CMS54 service monitor

TxDOT radio

Fluke 99B 'scope 12-V batteries Cable

Figure 7. Rolling EMI Measurement System Used for SAE J551/4 and TxDOT Tex-899-B Testing

One problem encountered in conducting the J55114 testing outdoors as we do, rather than in a shielded chamber, is noise emissions from the EMI receiver or spectrum analyzer. Over the years we have identified a few specific narrow-band emissions, using average detection to reduce the random, broad-band noise background. These are listed in Table 7. Such emissions are a real nuisance. The best way to identify them seems to be to use two different receivers listening to each other, switching each one on and off to identify its emissions.

18

Table 7. Spurious emissions from instrumentation

Receiver! Analyzer Amplitude Frequency dBJlV MHz

R&S ESS receiver - 17 47.56

R&S ESVP receiver -10 47.10

HP E7401A analyzer -7 46.97 -6 47.18 -6 47.39 -5 47.60

Of interest as potential noise sources were all of the DC motors on the trucks, that is, fuel pump, HV AC fan, windshield wiper, windshield washer, and light bar. J55114 peak values were measured with the ESVP receiver for various combinations of these motors on all five trucks. The values were found to range from 10 dBJlV to 60 dBJlV. The measurement bandwidth was 120 kHz. Average values were also measured on three of the trucks, those from ITU. Values ranged from the noise level at - 9 dBJlV to 3 dBJlV.

For comparison with the J55114 results, the Tex-899-B test was carried out on all five trucks. Values ranged from the noise level at about - 9 dBJlV up to just under the 0 dBJlV test limit.

After studying the test results on a case-by-case basis, our findings were as follows: (i) The data for these particular vehicles did not support the 40 dBJl V peak-detector limit

that was determined from laboratory simulation (Chapter n, end of Section A). In the laboratory this limit was found to coincide with the Tex-899-B SINAD test limit. But on the vehicles, it appeared to be too stringent. Two cases must be distinguished---- first, fuel pump, HV AC fan, and wipers running; and second, the previous three plus the windshield washer running. For the first case, the peak values were found to range up to 40 dBJlV, while the SINAD values all remained below their limit. Thus the 40 dBJl V limit looked as if it probably was too low for good correlation with the SINAD data. For the second case, the Dodge and Chevrolet (but not the Ford) showed large peak values, around 55 dBJlV, but the SINAD values were still below their limit. Thus here the 40 dBJl V limit definitely was too low. (But we had no way of knowing how much higher it should have been.)

This second case involved the operation of tiny windshield washer motors. Such motors were never tested in the laboratory because in normal vehicle operation they are used so briefly as to not merit inclusion in Tex-899-B testing. They were included in the vehicle tests for academic interest. As it turned out, they did indeed add some interest as they were the only motors which pushed the peak values above 40 dBJlV.

(ii) Some support was found in the vehicle tests for the average-detector limit of 3 dBJl V determined by laboratory simulation. The TTU Chevrolet gave the following results for all DC

19

motors turned on, including the washer: Tex-899-B FM signal = - 0.8 dB)lV; 155114 peak noise = 65.8 dB)lV; 155114 average noise = 3.0 dB)lV. Here we see a vehicle that just happens to fall on our 155114 average limit of3 dB)lV, and it lies only a fraction ofa dB under the Tex-899-B limit of 0 dB)l V, thus almost agreeing with the laboratory result (advantage (i), Chapter II, Section C).

(iii) There is evidence from all of the TTU trucks that the average detector gives such a weak response to spark-ignition noise that DC-motor noise can be measured with the engine running (advantage (ii), Chapter II, Section C).

Detailed presentations of our measurements of DC-motor noise are given in by 1. Yun [Appendix B] and P. Bahukudumbi [Appendix DJ.

A study of DC-motor noise which complements our own is described in a symposium paper by C. Suriano et al. [14]. They give information on the radio-frequency spectrum of the noise over the range 0.1 MHz to 1000 MHz.

C. Noise from Electronic Modules Using the ESVP receiver, noise emissions from electronic modules were checked with

the ignition key of the truck switched on, and everything else, engine and all accessories, switched off. The Dodge trucks proved to be by far the most interesting in this situation. As can be seen from the summary in Table 8, only the Dodges displayed a broad noise peak due to module emissions. We had not previously seen broad-band noise from modules, only narrow­band. Here we use the terms narrow-band (NB) or broad-band (BB) to mean narrow or broad compared to the TxDOT radio bandwidth of 15 kHz.

Table 8. Electronic-module emissions (46.9 Nlliz to 47.8 MHz)

Truck

Dodges Ford Chevrolet

Narrow-band Freq. (MHz)

47.38* 47.92 None observed

Broad-band Freq. (MHz)

47.34 - 47.44 None observed None observed

* The NB emission was superimposed on the BB, like a carrier with sidebands.

The time-domain signature of the noise from the Dodges was examined at 47.38 MHz. AM and FM waveforms ofthis noise were obtained by connecting the AM and FM outputs of the ESVP receiver to channels A and B of a Fluke 99B oscilloscope (battery powered, digital recording with 8-bit 25 MSals and 25 pixels/div display). Several waveforms observed on the screen were stored in the oscilloscope memories. Figure 8 shows the waveforms from memories

20

number 5 and 6. The sweep speed is 2 ms per division. The AM waveform shows two consecutive pulse trains, where the pulse period is 0.5 ms. The FM waveform does not reveal the pulses, but shows rapid noise fluctuations which seem to increase in amplitude during the time between the AM pulse trains. Arrows at the left show the zero-voltage level for each waveform.

~ l' 18.8V 7 2.88rns[!j l' 18.8V 7 2.88rns

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Figure 8. Oscillograph showing example of module noise from 1999 Dodge RAM2500 pickup truck

The frequency-domain signature of this noise was also examined. Figure 9 shows two frequency scans made with the ESVP receiver, one of the peak ambient noise level (ignition key OFF) and the other of the peak ambient-plus-module noise level (key ON). These scans were made one after the other with a measurement time of two seconds at each 5 k:Hz step. The three large spikes in the data are due to noise from vehicles driving past on the highway. The top of the module noise spectrum is quite flat and extends from about 47.34 MHz to about 47.44 MHz. The noise tapers off from this plateau rather unevenly on each side and persists weakly out to the edges of the graph, and perhaps well beyond.

What of the average level for this module noise? We re-measured across the top of the noise spectrum with the ESVP receiver, using both peak and average detectors, and the results are shown in Figure 10. Here we observe the interesting result that the peak-to-average ratio varies considerably; while the peak value forms a wide plateau, the average value contains a central peak with lowered sidebands.

21

An important question is how this noise-level data, which is J551/4 data, compares to SINAD or Tex-899-B data. To answer this question, we conducted the Tex-899-B test at three frequencies, 47.34 MHz, 47.38 MHz, and 47.42 MHz. The results are shown in Figure 11, where all three quantities are plotted-- peak and average from Figure 10 and SINAD. Here the SINAD data is seen to be well correlated, from one frequency to the next, with the average data but not with the peak data. This result points to the benefit of using average measurements in a J55114 test in order to achieve correlation with the Tex-899-B test. We return to this subject as part of our conclusions in Chapter V.

Switching the TxDOT radio's noise blanker on and off while the radio was tuned to the module noise had no effect on the SINAD value.

D. Vehicle PassIFail Results The details of the noise aside, it is important to know whether these trucks pass the Tex-

899-B test and thus should be accepted by TxDOT. In fact, four of the five trucks passed. The one which did not pass was the ITV Dodge. It failed at 47.34 MHz, which is the highest frequency in the TxDOT band. This truck was used for the data in Figures 10 and 11, and the failure is evident in Figure 11. As can be seen, the 12-dB-SINAD value at 47.34 MHz lies at 1 dB~V,just a slim 1 dB above the limit. It turned out that switching on DC motors- fuel pump, HV AC fan, and windshield wipers- contributed one additional dB. On the other hand, running the motors without the modules resulted in a pass. The culprit was the modules, not the motors. The failure occurred because the bottom end of the module-noise band was catching the top end of the TxDOT band. For the other two Dodges the module noise was shifted slightly higher in frequency, and they passed Tex-899-B.

22

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Radio Noise Emissions of 1999 Dodge Truck (TxDOT 2-S649-G) Measured with 10kHz Bandwidth

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23

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24

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25

E. Antenna Comparison In order to judge the importance of a change in antenna as far as the results of the Tex-

899-B test are concerned, three different antennas were used to measure module noise on the same Dodge truck with the same antenna mount and FM radio. The specifications of the truck, radio, mount, and antennas were as follows:

(i) Truck Make: 1999 Dodge RAM2500 V8 gasoline pickup truck owned by ITU Overall length: 5.61 m (26.7 MHz, 53.4 MHz, 80.2 MHz estimated resonances) Configuration: Key switched on Type of Noise: Electronic module

(ii) Radio Make: Motorola MaraTrac Frequencies: 47.34 MHz and 47.38 MHz

(iii) Antenna Base Make: MAXRAD Type: Magnetic mount, with 12 ft RG-58 AfU coaxial cable Location: Center of roof of cab

(i v) Antenna 1 Make: Spectrum Type: Base-loaded whip Comments: Currently supplied with MaraTrac radios

(v) Antenna 2 Make: Larsen NMO 50 (length = 1.33 m including base) Type: Base-loaded whip Comments: Many in TxDOT fleet; used for all testing by us at TTU

(vi) Antenna 3 Make: Custom-made at ITU Type: Quarter-wavelength whip Comments: Suggested by B. Rehm [14]

To check for proper antenna impedance matching before carrying out the Tex-899-B test, the return loss of each antenna was measured with an HP 8753C network analyzer. The results are shown in Table 9.

Table 9. Return-loss data for three antennas

Antenna Max. Return Loss Center Freq. Bandwidth* in dB inMHz inMHz

Spectrum 25 47.6 5.7 Larsen 18 47.6 7.6 Quarter -wavelength 11 47.6 8.4

* Bandwidth is defined as VSWR ~ 2.0 or return loss ~ 9.5 dB.

26

The results of the Tex-899-B test are shown in Table 10. Two frequencies were used. As evident from the table, all three antennas give about the same response . The output of the quarter-wavelength antenna is slightly lower than the rest probably because of its poor impedance-matching characteristics, as seen in the return-loss data. The close agreement between the base-loaded and non-base-loaded antennas observed here is apparently not consistent with results reported by B. Rehm [15].

Table 10. Tex-899-B results for three antennas

F. Questions

Antenna

Spectrum Larsen Quarter-wavelength

1. Current on outside of antenna cable

Tex-899-B Sig. Gen. Amplitude for 12-dB SINAD, in dBI-lV

47.38 MHz 47.34 MHz

14 14 13

- 1 - 1

-2

Unanswered questions always arise in research. Here are three, resulting from the vehicle test procedures.

There seems to be no standard procedure for choking off the undesirable current that can flow on the outside of the antenna cable in the J55114 and Tex-899-B tests. It may be larger and thus more of a problem when the test instrumentation is grounded. In our vehicle tests we used battery-powered equipment, which was not connected to AC power and thus not grounded.

Various experimenters have developed their own procedures. For example, Gus Morgan, author of Tex-899-B, describes using a large loop of cable covered by a sheet of hardware cloth [6]. 2. Surface below the vehicle

In the past, the vehicle-emissions part of the Tex-899-B test normally has been conducted outdoors with the vehicle-under-test parked in any convenient spot. On the other hand the J55114 test often has been conducted with the vehicle located inside an all-metal chamber (with RF absorber lining the walls and ceiling). Thus in one case the vehicle is tested over a surface of unknown electrical conductivity and in the other over one of very high conductivity. Whether this is an important difference is an open question. A related matter is vehicle resonance, which is described below. 3. Vehicle electromagnetic resonances

In analyzing the electromagnetic fields existing on, say, a pickup truck due to various onboard noise sources, one can imagine different types of behavior which fall into three regions [16]: the quasi-static region where the frequency of the sources is very low so that the length of

27

the truck is short compared to a wavelength, the resonance region where the truck is on the order of a wavelength in size, and the quasi-optical region where the frequency is so high that the truck is much longer than a wavelength. The trucks we have tested vary in length from about 17 feet to about 19 feet. For a wavelength equal to 18 feet, the frequency is 55 MHz. Thus, since our frequency of interest is the TxDOT communication band at 47 MHz, we see that in our case the trucks lie in the resonance region.

To a first approximation, the lowest resonance would occur when the truck is one-half wavelength long, at 27.5 MHz. The second resonance would be at one wavelength, 55 MHz, the third at 82.5 MHz, and so on.

We do not know how strong the resonance effects typically are for our trucks. The ground is lossy at these frequencies, which would cause some damping and lowering of Q. The general fatness of the truck bodies would broaden the resonances also. But the resonances would change somewhat, increasing in Q, if the truck were located on a conducting surface, a metal bridge for example. Computer modeling, like that described by F. Tesche et al. [17], would probably be a good way to investigate this effect.

In the event of a strong resonance, the position of the communications antenna on the truck would be critical. Located near a node in the resonant electric-field pattern, the antenna would pick up little noise, while near an antinode, the noise would be much stronger. For the one-wavelength resonance, which is the one closest to the TxDOT band, the antinodes are located at the front and back ends and the center of the truck. These would be undesirable locations for permanent mounting of the antenna. As a way of determining the actual strength of the resonance, it might be worthwhile to experiment with several different antenna locations.

G. Diesel Truck As part of our measurement campaign, we tested one diesel-powered truck. It was a brief

test, carried out at the TxDOT radio shop in Lubbock in response to a call from Leonard Bryan. The truck was a 1999 Chevrolet 3500 HD, TxDOT 5-5336-0 (VIN IGBKC34F3XF097674). The measurements consisted of spectrum'scans with the HP EMC analyzer connected to the truck's antenna. They revealed a strong, narrow-band emission with the truck in the key-on condition and in the engine-running condition-- obviously a module-noise problem. Amplitude was about 27 dB~V and frequency about 47.02 MHz. Unfortunately the emission lay on the lowest TxDOT frequency, the one mainly used in Lubbock. The truck clearly would not have passed the Tex-899-B test, being 30 dB above the limit for module noise.

Mr. Bryan, working with the local Chevrolet dealer, traced the problem to the module that monitors and controls the level of fuel in the truck's two tanks. A solution to the problem is still being sought as of this writing.

H. Limit on Electric Field Strength For completeness we mention some EMC industry standards in addition to SAE 1551/4.

FCC Title 47 Part 15, CISPR 22, SAE 155112, and MIL-STD-461D specify limits on the electric field strength of emissions. These standards are of some relevance for us because the TxDOT whip antennas are sensitive to the electric field, rather than the magnetic. However they are not useful in our situation for a number of reasons, some or which are given by Kimmel and Gerke [18]. If we were to specify a limit on electric field, it would be on the order of 1 ~ V Im for CW

28

emissions since we can use E:::: V/I and our J55114 limit on voltage is on the order of l!l V and our antenna is about 1 m long. A book of general interest in the area of EMC testing and limits is that by K. Javor [19].

29

IV. SURVEY OF STATE DEPARTMENTS OF TRANSPORTATION

As part of Phase II, Prof. Mehrl conducted a survey of departments of transportation around the country. The objectives were to find out how many vehicles equipped with low-band mobile radios were in service and to learn what vehicle-generated interference problems have been experienced, that is, to see to what extent problems like TxDOT's existed beyond the borders of Texas. Compilation of the numbers supplied by the survey respondents gave a total of about twenty-eight thousand radios in use, of which about five thousand were in Texas. Many responses revealed vehicle RFI problems, and solutions or the lack thereof, similar to the experiences ofTxDOT. The survey responses are included in Appendix E.

During the last briefing by Prof. Trost and Mr. Lewis to the SAE EMR Committee, i.e . the TEAM, in January 2001, copies of the survey responses were handed out. The intent was to make the committee members aware of the true extent of the low-band situation, and to provide added impetus to the vehicle manufacturers for eliminating the problems in the future.

To inform the state DOTs about our work on this project, each state DOT that participated in the survey was mailed a copy of Tex-899-B [Appendix B (appendix)], Prof. Trost's symposium paper [Appendix C], and the survey results [Appendix El

30

V. CONCLUSIONS

A. A Pattern for Peak and Average Limits We gathered together all the various results from laboratory and vehicle tests, including

peak and average amplitude data from the EMI receiver and SINAD data from the FM radio; and we looked for evidence of an underlying pattern. We had in mind that a key ingredient in this complicated mix of data is how the radio behaves when teased by the various vehicle noise sources. The behavior depends in large part on the characteristics of the radio's FM detector and noise blanker.

We imagined characterizing all of the noise sources, electronic-module, DC-motor, and spark-ignition, according to their peak-to-average ratios (or crest factors). When we plotted out our proposed peak and average limits versus noise source peak-to-average ratio, a pattern indeed emerged. The resulting graph is shown in Figure 12. Lines have been drawn in to connect the data points and thus reveal the pattern formed by the splitting and curving apart of the two limits from their common value at the left. Notice that, according to the legend, the abscissa is divided into electronic-module noise at the left followed by DC-motor noise and then spark-ignition noise. The module noise occupies the range of 0 dB to 14 dB peak-to-average ratio; the motor noise from 14 dB to 36 dB; and the ignition from 36 dB to 44 dB. The peak-to-average ratio of 0 dB represents CW noise, such as a harmonic from a microcontroIler clock, which has the same peak and average values. The splitting of the limit lines at the left is due to the response of the radio's FM detector to the pulsed AM noise of the modules; the upward curving of the lines at the right is due to the radio noise blanker which removes some of the noise pulses thus allowing the radio to tolerate a greater noise amplitude for a 12 dB SINAD.

The four data points near the center of the plot, those at peak-to-average values of 12 dB and 24 dB, were extracted from Figure 11.

The two coincident data points at the left edge come from our laboratory studies, where we simulated vehicle CW noise (the easiest kind to simulate).

The two data points on the right at the value of 32 dB peak-to-average were taken from a laboratory simulation by P. Bahukudumbi [Appendix DJ. Note that the 40 dBJlV value quoted often above in this report as the peak limit for DC-motor noise applies to a measurement bandwidth of 120 kHz, and in Figure 11 the bandwidth is 9 kHz, so the peak limit is lower, as is the average limit.

There is also some laboratory data obtained by Y. Jin [20] which fits the pattern of these diverging curves. It comes from one of our Phase I experiments that was motivated by an observation of module noise kindly supplied to us by the EMC laboratory at General Motors. The noise was pulsed AM but with a simpler frequency spectrum than the module noise from the Dodges described above. Jin's values are -2 dBJlV (Pk) and -8 dBJlV (avg) at 6 dB peak-to­average and -1 dBJlV (Pk) and -14 dBJlV (avg) at 14 dB peak-to-average.

31

Limit-Line Trajectories 9 kHz Measurement Bandwidth

30~==========~======~--~----------1I.~---------r----1 • Average Limit

- • Peak Limit > 20 ::::L III

- . Module Noise Range "C - - - DC-Motor Noise Range (J) .~

E 10 ::i

- - - Ignition Noise Range

..::.::: ca Cl) c.. "C 0 I: ca Cl) C'I ca a.... Cl) -10 > «

-20 +-----~------~------~-----+------~----~------~------+-----~ o 10 20 30 40

Noise Peak-to-Average Ratio (dB)

Figure 12. Trajectories of peak and average limits

32

B. Options for Testing New Vehicles for TxDOT Service We have identified three vehicle noise sources, as shown in Figure 12: module, DC­

motor, and ignition. However the TxDOT radios are immune to ignition noise, so that only module and DC-motor noise need be discussed. Between the two, it is likely that the module noise is the more important; it is the only type of noise that caused a vehicle to fail the Tex-899-B test in our testing campaign this past year, and in the future one can expect to find more modules, that is to say more electronic devices, on the vehicles, increasing the likelihood of interference to TxDOT radios. On the other hand, motor noise would seem to be the easier to suppress because it occurs on DC lines not signal lines, and it is currently being subjected to increasing attack from RF-suppression filters, such as the new chip filters made by Syfer Technology Limited in England.

As far as the module noise is concerned, one can see from the upper curve in Figure 12 that the J55114-type limit on the peak value rises as one considers noise with higher peak-to­average ratios. In order to apply such a variable limit to a vehicle-under-test, one would need to measure both peak and average values, compute their ratio, and determine the appropriate limit by reference to the curve. (And one would of course prefer a better-defined curve, one with more points on it.) This procedure looks fine in principal, but in practice it would be somewhat time-consuming and perhaps confusing to the test operator, requiring two measurements and a computation. It might be just as well to carry out the SINAD test instead. An alternative, of the J55114 type, which would be fast and simple, would be to just measure the peak value and apply the -3 dB)l Y limit, regardless of what peak-to-average the noise in question might have. This would amount to applying an accurate limit if the noise were CW but applying too stringent a limit if the noise were pulsed. But it would be just like the J551/4 tests currently run in the automotive industry in the sense that it would consist of a quick peak scan and superimposed limit line.

As far as DC-motor noise is concerned, we spent a good deal of time in a laboratory investigation, operating an HV AC fan and two fuel pumps with Stoddard solvent in a fume chamber. But it was rather frustrating work. Peak noise values were quite variable; in addition to motor-aging and battery-voltage variations, there was always a statistical variation with 2 dB standard deviation. On the test vehicles the noise was difficult to study because it was never strong enough, by itself, to cause a failure in the Tex-899-B test. The new limits we found for the J55114 test, 40 dB)lY peak and 3 dB)lY average, are based largely on the laboratory measurements. These limits apply, by the way, when using a measurement bandwidth of 120 kHz, which is appropriate for very broad-band emissions like DC-motor noise.

Our options then appear to be threefold: a SINAD test, a modified J55114 test with peak limits only, and a modified J55114 test with peak and average limits. But, as we now explain, we must hold off on the average-detection option. Two published standards for average detectors are known to us; they are contained in CISPR 16-1 [12] and VDE 0876 Part 3 [21]. These standards require that average detection be reasonably accurate for noise with pulse rates (or frequencies) down to 5000 pps. This value is probably not low enough for our purposes since we have observed vehicle emissions with pulse rates in the range 50 pps to 2000 pps. Information on the specific average detector in the ESVP receiver is contained in the Operating Manual [22]. It indicates that the detector is accurate for pulse rates down to about 1000 pps when using the 120 kHz bandwidth. Our data in Figure 5 do not agree with this. By comparing the various R&S curves with the theoretical, one can see a lower-frequency limit of perhaps 2000 pps. The HP curve with pre-amplifier switched off actually looks more consistent at lower

33

frequencies than the R&S. In any case, in order to make average detection a routine part of TxDOT testing, a more thorough study of average detector standards and performance will be required.

Thus we suggest to the automakers, as a test for new vehicles destined for TxDOT service, either of the two remaining options, SINAD or J55114 with peak only. We have incorporated these options into a single detailed test procedure, which is included as Appendix A. This procedure is in fact an expanded version of the original Tex-899-B test, in which the new J55114 peak-only test is included. Other imp0I1ant improvements over the original version of Tex-899-B have also been made. A summary of our changes to Tex-899-B is given in the following section.

C. Expanded Tex-899-B Test Our various draft changes to Tex-899-B are listed below. For the reader who wishes to

examine the original Tex-899-B and SAE J551/4 documents, copies as included as appendices in the thesis by J. Yun [Appendix B]. (i) Optional J551/4 testing

A modified version of J55114 was included as an alternative to the SINAD test. The modifications to J55114 include changing the narrow-band limit from 0 dBIlV to - 3 dBIlV and applying it to module noise, and changing the broad-band limit from 28 dBIl V to 40 dBIl V and applying it to DC-motor noise. The modified test thus looks like that shown in Table 1 in Chapter IT, with the word "NB" deleted from the phrase "NB electronic-module emissions" in the Conunent column. (ii) SINAD testing

a. The combination of a 6 dB degradation limit and a 1 11 V maximum-signal limit was replaced with just the 1 J.l V limit.

b. An option was included whereby the FM signal generator does not have to be adjusted for a 12-dB SINAD reading for each test condition but can be left at the setting corresponding to the 1 11 V limit. This procedure results in a faster test. If the observed SINAD value is greater than 12 dB, the vehicle passes; if less than 12 dB, it fails. The signal amplitude required to bring the SINAD reading to 12 dB is not determined. This amplitude can be roughly estimated, but the variation in amplitude with SINAD value is a nonlinear one and depends somewhat on the type of vehicle noise being measured and on the ambient noise level. The nonlinearity is the result of the threshold effect [23] of the FM detector and is such that the SINAD value changes with signal amplitude more strongly in the vicinity of the 12 dB point than away from it.

The time-intensive nature of the original procedure was cited as a major drawback of the SINAD test from the point of view of the automakers . The new, faster procedure addresses this complaint.

c. The requirement was added that the TxDOT radio noise blanker must always be turned on during testing. This requirement was recognized early on in our vehicle tests [24]. (iii) Frequency range

The required range of testing frequencies was extended to include not only the TxDOT radio channels but also a number of frequencies between, above, and below. This change was made because it had been found [15] that narrow-band vehicle emissions lying near a TxDOT channel can, over the course of time, drift squarely onto it. (iv) Miscellaneous changes

34

a. A Table of Contents was added. b. Many additional details were included in the Equipment List. c. Numerous minor changes in wording were made throughout.

D. Future Directions One obvious avenue of research to pursue in the future is a comprehensive investigation

of average detectors, their performance for various noise waveforms and their limitations. The inclusion of average detection in motor-vehicle emissions testing, as in our third option mentioned above in Section B, may prove to be an excellent technique, or it may force existing EMI receivers to work at or beyond their measurement limits, thus negating the potential benefit. And perhaps more rigorous standards are needed for average detection, as suggested by Poul Andersen at the January 2001 meeting of the SAE EMR Committee meeting.

It would also be worthwhile to answer the questions posed in Chapter In, Section F. It is hoped that the vehicle manufacturers will put to use the expanded Tex-899-B test

developed during this project. Time will tell to what extent EMC problems will decrease for TxDOT. But some kind of follow-up consultation with the manufacturers seems advisable, in order to discover their experience in testing their new models vis-a-vis the TxDOT requirements.

Along with the sharing of specific technical knowledge between TxDOT and the manufacturers, new paths of communication and personal relationships have grown out of the present project. These will serve to work to everyone's mutual interest.

Twelve states participated in our survey of low-band-VHF users; and, having established this database of other states with concerns similar to TxDOT's, it may be advantageous for TxDOT to set up some sort of ongoing cooperative activity. We have not made full use of all the information that is available from these other states. Perhaps some form of electronic clearinghouse for RFI information, problems and fixes, would be worthwhile.

The future of motor vehicle design undoubtedly holds new EMC challenges. But it may be that some help is on the way for TxDOT as a result of the myriad of new RF accessories that will be appearing on the future vehicles- e.g. telephones, navigation systems, traffic avoidance systems. These accessories will demand very low vehicle emissions over a very broad frequency range, including the TxDOT band. Thus a more comprehensive effort will be devoted to EM noise reduction by the vehicle manufacturers.

There is also the inverse issue, the vehicle susceptibility to the accessories. In the case of TxDOT, the problem of vehicle susceptibility to the radio transmitter has diminished in recent years, but it could undergo a resurgence in the future. It is a two-way street; as one author put it, " ... VHF radios and microprocessors are mutual antagonists" [18].

The SAE standard J55114 has been harmonized with the international standard CISPR 25 [25]. So the modifications we made to J55114 in order to include it in Tex-899-B could find their way in some form into CISPR standards also.

35

REFERENCES

1. Trost, Thomas F., "Testing for FM-Radio Interference in Motor Vehicles," final report on TxDOT research study No. 7-2995, December 1998.

2. Smith, AlbeIt A., Radio Frequency Principals and Applications, p. 149, IEEE Press, New York, NY, 1996.

3. NAVAlR AD 1115, "Electromagnetic Compatibility Design Guide for Avionics and Related Ground Support Equipment," 3rd Ed., Department of the Navy, June, 1988.

4. White, Donald, R.J., A Handbook on ShieLding Design Methodology and Procedures, Interference Control Technologies, Gainesville, V A, 1986.

5. Clark, T.L., M .B. McCollum, D.H.Trout, and K. Javor, "Marshall Space Flight Center Electromagnetic Compatibility Design and Interference Control (MEDIC) Handbook," Huntsville, AL, June, 1995.

6. Test Method Tex-899-B, "Radio Frequency Interference (RFJ) Testing," Texas Department of Transportation, Austin, TX, 1995.

7. Surface Vehicle Standard SAE J551/4, "Test Limits and Methods of Measurement of Radio Disturbance Characteristics of Vehicles and Devices, Broadband and Narrow band, 150 kHz to 1000 MHz," Society of Automotive Engineers, Warrendale, PA, 1994.

8. TIAfEIA Standard TIAlEIA-603, "Land Mobile FM or PM Communications Equipment Measurement and Performance Standards," Distortion, SINAD, and audio-frequency level meter, 1.5.1 (pp. 16-17), Reference Sensitivity, 2.1.4 (pp. 37-38), Telecommunications Industry Association, Washington, DC, Feb. 1993.

9. Jin,Ye, "Laboratory Simulation of Motor Vehicle Radio Interference," Master's Thesis, Electrical Engineering Department, Texas Tech University, Lubbock, TX, 1998.

10. Herndon, Richard, TxDOT, Austin, private communication, 2000.

11. TIAlEIA Standard TIAlEIA-603, "Land Mobile FM or PM Communications Equipment Measurement and Performance Standards," Impulse Blanking Effectiveness, 2.1.18 (pp. 53-54) and 3.1.18 (pp. 123-124), Feb. 1993.

12. CISPR 16-1, "Specification for radio disturbance and immunity measuring apparatus and methods, Part 1: Radio disturbance and immunity measuring apparatus," International Electrotechnical Commission, Geneva, Switzerland, 1999.

13. Rudin, Walter, Real and Complex AnaLysis, p. 61, McGraw-Hill, New York, NY, 1966.

36

14. Suriano, Candace R. et al., "Prediction of Radiated Emissions from DC Motors," IEEE EMC Symposium, pp. 790-795, Denver, CO, August 24-28,1998.

15. Rehm, Bradford, Professional Testing, Inc ., Round Rock, plivate communication, 2000.

16. Lee, K.S.H., "EMP Interaction: Principles, Techniques, and Reference Data," AFWL-TR-80-402, Chapter 1.4, Air Force Weapons Laboratory, Albuquerque, NM, 1980.

17. Tesche, Frederick M. et al., EMC: Analysis Methods and Computational Models, John Wiley and Sons, New York, NY, 1997.

18. Kimmel, William D. and Daryl D. Gerke, EM! Suppression Handbook, p. 77, Seven Mountains Scientific, Boalsburg, PA, 1998.

19. Javor, Ken, Introduction to the Control of Electromagnetic Interference, EMC Compliance, Huntsville, AL, 1993.

20. Jin,Ye, "Laboratory Simulation of Motor Vehicle Radio Interference," Master's Thesis, p. 52, Electrical Engineering Department, Texas Tech University, Lubbock, TX, 1998.

21. VDE 0876 Part 3, "Radio Intelference Measuring Receiver with Average Value Indication," Verband der Elektrotechnik Elektronik Informationstechnik e.V., Frankfurt, Germany, 1987.

22. Operating Manual for Test Receiver ESVP, pp. 2.104.1-2.104.3, Rohde & Schwarz, Munich, Germany, 1985.

23. Schwartz, Mischa et al., Communication Systems and Techniques, p. 138, IEEE Press, New York, NY, 1996.

24. Zhou, Qianlin, ''Testing Motor Vehicle for Radio Interference," Master's Thesis, p. 50, Electrical Engineering Department, Texas Tech University, Lubbock, TX, 1998.

25. CISPR 25, "Limits and methods of measurement of radio disturbance characteristics for the protection of receivers used on board vehicles," International Special Committee on Radio Interference, International Electrotechnical Commission, Geneva, Switzerland, 1995.

37

Appendix A: Expanded Tex-899-B Test

1.

II.

IIl.

IV.

V.

VI.

Test Method Tex-899-B (Trost Draft)

RADIO-FREQUENCY INTEFERENCE (RFI) TESTING

February 2001

This test method assures the compatibility of Texas Department of Transportation (TxDOT) fleet vehicles and VHF FM radio equipment operating in the frequency ranges of 30 to 50 MHz and 150 to 174 MHz. It is intended to identify 90 % or more of RFI ingress and egress problems.

Contents DEFINITIONS

EQUIPMENT

F ACll.lTIES

SAFETY NOTES

INGRESS COMP A TIBII..JTY A. Antenna Qualification B. Ingress Compliance Test for Vehicle C. Vehicle Ingress Qualification

EGRESS COMPATlBII..ITY A. Antenna Qualification B. Radio Receiver Qualification C. SINAD Test Options D. Site Qualification

1. Measurements 2. Effective Sensitivity Calculation

E. Egress Compliance Test for Vehicle F. Site Qualification- Faster Method G. Egress Compliance Test for Vehicle- Faster Method H. Vehicle Egress Qualification

1

2

2

3

3

4 5 5

6 6 7

8 9

10 11 12 12

VII. EGRESS COMPATIBII..JTY- ALTERNATE METHOD A. Antenna Qualification 13 B. Egress Compliance Test for Vehicle, Using Modified SAE Test 13 C. Vehicle Egress Qualification 13

VID. VEHICLE QUALIFICATION FOR ACCEPTANCE 13

I. DEFINITIONS Ingress (vehicle electromagnetic susceptibility): Any action, reaction, indication,

or failure to perform or comply by vehicle equipment and/or accessory items caused by the activation of the VHF FM radio transmitter in any mode of operation

Egress (vehicle electromagnetic emission): Any mode of operation, action, reaction or indication by the vehicle equipment and/or accessory equipment which degrades the VHF FM radio receiver effective sensitivity

IT. EQUIPMENT The following instrumentation is required if sections V and VI are to be carried

out. However if section V1I is substituted for section VI, then items 3, 4, 5, and 6 are omitted and an EM! receiver or spectrum analyzer, as specified in SAE 1551/4 and CISPR 16-1, is required instead. (SAE 1551/4: ''Test Limits and Methods of Measurement of Radio Disturbance Characteristics of Vehicles and Devices, Broadband and Narrowband, 150 kHz to 1000 MHz," Society of Automotive Engineers, Warrendale PA, USA, May 2000. CISPR 16-1: "Specification for radio disturbance and immunity measuring apparatus and methods, Part 1: Radio disturbance and immunity measuring apparatus," International Special Committee on Radio Interference, International Electrotechnical Commission (IEC), Geneva, Switzerland, 1999 [available from American National Standards Institute (ANSn, New York NY, USA].)

1. 100-W VHF FM communications radio (transceiver) capable of operating on all frequencies of interest, such as Motorola MaraTrac, with noise blanker switched on. TxDOT low-band VHF channels lie at 47.02,47.04,47.06,47.08,47.10,47.12,47.14, 47.16,47.18,47.20,47.22,47.24,47.26,47.34 MHz.

2. 12-V DC power supply or 12-V battery for radio 3. FM signal generator 4. Signal-to-noise-and-distortion (SINAD) meter, as specified in "Land Mobile

FM or PM Communications Equipment Measurement and Performance Standards," ANSI TIAfEIA-603-1992, Telecommunications Industry Association, Washington DC, USA, February 1993, Section 1.5.1

5. Audio load for radio 6. RF matched three-port coupler with one low-attenuation path, such as a

directional coupler with less than 1.2 VSWR, less than 0.5 dB attenuation, about 20 dB or higher coupling, and greater than 20 dB directivity and all parameters essentially constant over the range of test frequencies

2

7. RF low-power coaxial load 8. Whip antenna with magnetic mount for frequencies of interest 9. Coaxial cable (RG-58 or similar) of sufficient length to reach from the vehicle

under test to the test instrumentation . See Figure 1. If the test results are found to be sensitive to the position of the cable or the instrumentation, a suitable external RP choke should be employed. Such a choke could consist of several ferrite beads on the cable or of a 6 ft by 6 ft (1.8 m by 1.8 m) sheet of hardware cloth, laid flat on the test area floor with the coaxial cable making one complete loop approximately four feet in diameter under it

10. RP directional watt meter for radio

Ill. F ACll..JTIES 1. Free of high ambient RF noise (for egress test) 2. Providing for rotation of vehicle wheels, such as, for example, by raising the

vehicle off the floor (for ingress test) 3. Free of large nearby metal objects, except possibly the floor, unless they are

covered with RP-absorbing material (for both tests)

IV. SAFETY NOTES Safety must never be compromised during tests. Hazards exist due to moving

vehicle parts, exposed electrical wires, and electromagnetic radiation. Strict compliance with accepted work practices must be observed at all times. Sudden actions may result when the radio transmitter is activated. Stay clear of vehicle and antenna. One person should operate the vehicle, and another the radio.

3

V. INGRESS COMPATIBILITY A. Antenna Qualification

Step Action

1 Locate vehicle at a suitable test site. (See FACILITIES.)

2 Assemble test setup as shown in Figure 1. Solid arrows in figure show signal path .

3 Verify engine is switched off.

4 Provide for rotation of vehicle wheels.

5 Place magnetic-mount antenna in center of vehicle roof. *

6 Key microphone on radio.

7 Record forward RF power to the antenna.

8 Record reflected RF power from the antenna.

Adjust length of antenna, if needed, and repeat steps 6 through 8 9 until forward power is 100 W ± IOW and reflected power is less

than 10 % of forward power on all TxDOT channels of interest.

* On some vehicles the roof may be obstructed so that an alternate antenna location, consistent with good radio communications, is required.

The antenna is qualified when the reflected power is less than 10 % of the forward power on all TxDOT channels of interest.

Antenna ~

'-_o_n_v_e_hi_CI_e ............... 1---- c~:ke

.... Coaxial Cable

RFWatt I Radio ~ .... Meter

... .... Coaxial ..... Coaxial I

Cable Cable

I Not less than 1 0 It r horizontal dista 13m)~ DC Power

Supply nee

Figure 1. Setup for Antenna Qualification and Ingress Compliance Test

4

B. Ingress Compliance Test for Vehicle

Step Action

1 Setup same as in Figure 1. Start vehicle engine.

2 Put vehicle in gear and rotate tires at a moderate speed.

3 Activate one vehicle system or accessory. Be certain to check the braking operation.

4 Activate the radio transmitter for approximately five seconds.

Record results as one of the following:

5 1. No adverse reaction. 2. Reaction resulting in safety hazard. 3. Reaction resulting in a nuisance operation.

6 Repeat steps 3 through 5 until all vehicle systems and accessories are activated.

7 Repeat vehicle qualification for all radio channels to be used.

8 Stop wheels of vehicle and turn off engine.

C. Vehicle Ingress Qualification The vehicle under test passes the ingress compliance test when no reactions occur

which result in a safety hazard or a nuisance operation.

5

VI. EGRESS COMPATIBILITY A. Antenna Qualification

The antenna qualification procedure described above in INGRESS COMPATIBILITY serves also to qualify the antenna for egress compatibility testing.

An alternative to this procedure is to use an RF network analyzer instead of the radio and power meter to measure the reflected power and insure that it is less than 10 % of the incident power at the frequencies of interest.

B. Radio Receiver Qualification

Step Action

1 Assemble test setup as shown in Figure 2.

2 Generate a standard signal (on-channel FM with 1.0 kHz sinewave tone at ± 3.3 kHz deviation) on first test frequency.

3 Vary signal amplitude to establish 12 dB SINAD.

4 Record signal amplitude, that is, receiver basic sensitivity, In

dB).tV.

5 Increase signal 6 dB above that in step 4.

6 Increase peak deviation until SINAD is degraded to 12 dB.

7 Record receiver modulation acceptance (bandwidth).

8 Repeat steps 2 through 7 at all remaining test frequencies. (See NOTE 1 below.)

NOTE 1: Test frequencies should include TxDOT channel frequencies plus additional nearby frequencies, in order to detect possible vehicle emissions that, over the course of time, could drift onto TxDOT channels. For the TxDOT frequency band from 47.020 MHz to 47.340 MHz, 61 test frequencies, spaced 10 kHz apart, are required as follows: 46.880, 46.890, 46.900, 46.910,46.920, 46.930, . .. ,47.430,47.440,47.450,47.460,47.470,47.480 MHz.

The receiver is qualified for vehicle acceptance testing if the following conditions hold at all test frequencies:

l. The receiver basic sensitivity value is less than - 8 dB/LV (0.4 /LV) for 12 dB SINAD.

2. The receiver bandwidth is a minimum of ± 6.5 kHz and a maximum of ± 8.0 kHz.

6

FM Signal ... Radio ...I Audio Load I Generator Coaxial

... RX Audio

~ L

I • Cable Cable

DC Power SINAD Meter Supply

Figure 2. Setup for Receiver Qualification

C. SINAD Test Options To complete sections D and E below, a large number of SINAD measurements is

required because of a mUltiplicity of frequencies and vehicle conditions. According to the steps shown, in each measurement one adjusts the FM signal generator to give a 12-dB SINAD reading and then records the signal generator amplitude. From this amplitude one calculates the receiver effective sensitivity. After completing the measurements for Site Qualification, one checks to see if all of the receiver effective sensitivity values lie below the - 6 dBIlV limit; and after completing the measurements for Egress Compliance, one similarly checks to see if all of the receiver effective sensitivity values lie below the 0 dBIl V limit.

The process of adjusting the signal generator for 12 dB SINAD on each measurement is time consuming, but it gives one the effective sensitivity and thus allows one to know the dB difference between the effective sensitivity and the limit. If one does not care about the value of this difference but only whether the limit is exceeded and if furthermore the performance of the RF coupler does not vary over the test frequencies, one can save time by employing an alternate measurement procedure that does not require the adjustment for 12 dB. This faster measurement procedure is given in sections F and G as an alternative to the procedure in sections D and E.

7

D. Site Qualification 1. Measurements

Step Action

1 Locate vehicle at a suitable test site. (See FACILITIES.)

2 Assemble test setup as shown in Figure 3. Low-attenuation path of coupler is between radio and antenna or load.

3 Verify that magnetic-mount antenna is located in center of vehicle roof.

4 Disconnect the vehicle battery cable.

5 Terminate the RF line into the RF load.

6 Generate a standard signal (on-channel FM with a 1 kHz sinewave tone at ± 3.3 kHz deviation) on first test frequency.

7 Increase the signal generator RF output level until a 12 dB SINAD indication is achieved.

8 Record signal amplitude, that is, sensitivity into RF load, in dBJ,tV.

9 Disconnect load and connect antenna.

10 Increase signal generator RF output level until a 12 dB SINAD indication is achieved.

11 Record sensitivity into antenna in dBJ,tV.

12 Compute and record the effective sensitivity, using steps in Table (Effective Sensitivity Calculation) below.

13 Repeat steps 5 through 12 at all remaining test frequencies. (See NOTE 1 under Radio Receiver Oualification above.)

8

Antenna on Vehicle

RF Load

.. . ~

Coaxial Cable

RF Coupler

A~ Coaxial Cable

FM Signal Generator

Audio .. Radio .. Load Coaxial ~ RX Audio~ Cable Cable

."

DC Power SINAD Supply Meter

Figure 3. Setup for Site Qualification and Egress Compliance Test

2. Effective Sensitivity Calculation

Step Action

1 Subtract sensitivity into load from sensitivity into antenna.

2 Record this difference.

3 Add this difference to the receiver basic sensitivity in dB/LV.

4 Record the receiver effective sensitivity in dB/L V.

The site is qualified if the receiver effective sensitivity value is less than - 6 dE/LV (O.S/LV) at all test frequencies.

9

E. Egress Compliance Test for Vehicle

Step Action

1 Setup same as Figure 3, with antenna connected. Reconnect the vehicle battery cable.

2 No vehicle systems are activated. Increase the signal generator RF output level until a 12 dB SINAD indication is achieved.

3 Record the signal generator RF output level.

4 Activate one vehicle system or accessory.

5 Increase the signal generator output level until a 12 dB SINAD indication is achieved.

6 Record the signal generator RP output level.

7 Repeat Steps 4 through 6 until all vehicle systems and accessories are activated.

8 Compute and record the effective sensitivity as in Table (Effective Sensitivity Calculation) above.

9 Repeat steps 2 through 8 at al1 remaining test frequencies. (See NOTE 1 under Radio Receiver Oualification above.)

10 Turn off engine.

10

F. Site Oualification- Faster Method

Step Action

1 Locate vehicle at a suitable test site. (See FACrrJTIES.)

2 Assemble test setup as shown in Figure 3. Low-attenuation path of coupler is between radio and antenna or load.

3 Verify that magnetic-mount antenna is located in center of vehicle roof.

4 Disconnect the vehicle battery cable.

5 Terminate the RF line into the RF load.

6 Generate a standard signal (on-channel FM with a 1 kHz sinewave tone at ± 3.3 kHz deviation) on first test frequency.

7 Increase the signal generator RF output level until a 12 dB SINAD indication is achieved.

8 Record signal amplitude in dB,uV.

9 Subtract from this value the value in step 4 of Radio Receiver Oualification and then add - 6 dB,uV.

la Set signal generator RF output level to this value.

11 Disconnect load and connect antenna.

If SINAD meter reading is less than 12 dB, the site exceeds the 12 limit; if greater than 12 dB, the site does not exceed the limit.

Record result.

13 Repeat step 12 at all remaining test frequencies. (See NOTE 1 under Radio Receiver Oualification above.)

The site is qualified if the SINAD meter reading is greater than 12 dB at all test frequencies.

11

G. Egress Compliance Test for Vehicle- Faster Method

Step Action

1 Setup same as Figure 3, with antenna connected. Reconnect the vehicle battery cable.

2 Increase the signal generator RF output level by 6 dB from the value set in step 10 in Site Oualification- Faster Method above.

No vehicle systems are activated. If SINAD meter reading is less 3 than 12 dB , the vehicle exceeds the limit; if greater than 12 dB , the

vehicle does not exceed the limit. Record result.

4 Activate one vehicle system or accessory.

If SINAD meter reading is less than 12 dB, the vehicle exceeds the 5 limit; if greater than 12 dB, the vehicle does not exceed the limit.

Record result.

6 Repeat Steps 4 and 5 until all vehicle systems and accessories are activated.

7 Repeat steps 3 through 6 at all remaining test frequencies. (See NOTE 1 under Radio Receiver Qualification above.)

8 Turn off engine.

H. Vehicle Egress Oualification The vehicle under test passes the egress compliance test when the effective

sensitivity value does not exceed 0 dBJ.tV (1.0 J.tV}- or in the faster method when the SINAD meter reading is greater than 12 dB- for all modes of operation, which includes engine off, engine on, (from idle to partial throttle), and all vehicle systems or any combination thereof.

12

VII . EGRESS COMPATIBILITY-ALTERNATE METHOD A. Antenna Qualification

The antenna qualification procedure described above in INGRESS COMPATIBILITY serves also to qualify the antenna for egress compatibility testing.

An alternative to this procedure is to use an RF network analyzer instead of the radio and power meter to measure the reflected power and insure that it is less than 10 % of the incident power at the frequencies of interest.

B. Egress Compliance Test for Vehicle, Using Modified SAE Test An alternative to the SINAD test specified above in section VI is a modified

version of the test described in SAE Standard J551/4. See EQUIP"MENT. This is not a SINAD test but rather an RF noise emissions test. The FM signal generator, RF coupler, SINAD meter, and audio load are not required. Instead an EM! receiver or spectrum analyzer, as specified in J55114 and CISPR 16-1, is used. The J551/4 procedure should be followed with the following modifications:

1. The flow chart in FIGURE 1 and the limits in TABLE 1 of J551/4 are not used.

2. The limit of noise emissions from vehicle electronic modules = - 3 dBjL V measured with an EM! receiver or spectrum analyzer with 9 kHz bandwidth connected to the antenna on the vehicle. Module emissions can be measured with the ignition key switched on but engine and all DC motors off. DC motors include those used in fuel pump, HV AC fan, windshield wipers, radiator fan, and electric windows.

3. The limit of noise emissions from vehicle DC motors = 40 dBjLV measured with an EM! receiver or spectrum analyzer with 120 kHz bandwidth connected to the antenna on the vehicle. DC-motor emissions should be measured with all DC motors running (only driver's electric window).

4. Since according to J55114 the ambient noise emission levels must be at least 6 dB below the vehicle limits and in view of the modified vehicle limits specified in 2 and 3 above, the ambient limits are - 9 dBjLV and 34 dBjLV, respectively.

Emissions should be measured at each TxDOT channel frequency of interest plus additional nearby frequencies as mentioned in NOTE 1 in Radio Receiver Qualification. For the TxDOT frequency band from 47.020 MHz to 47.340 MHz, the range 46.980 MHz to 47.380:MHz must be scanned. Peak detection is to be used, with a measurement time of two seconds at each frequency.

C. Vehicle Egress Qualification The vehicle under test passes the egress compliance test when it meets these

limits at all test frequencies.

VID. VEHICLE QUALIFICATION FOR ACCEPTANCE The vehicle passes the Tex-899-B test and is qualified for acceptance if it passes

the ingress compliance test and one of the egress compliance tests.

13

Appendix B: MSEE Thesis by Jongsin Yun

LABORATORY SIMULATION OF MULTIPLE SOURCES

OF MOTOR VEHICLE RADIO INTERFERENCE

by

JONG-SIN YUN, B.E.

A THESIS

IN

ELECTRICAL ENGINEERING

Submitted to the Graduate Faculty of Texas Tech University in

Partial Fulfillment of the Requirements for

the Degree of

MASTER OF SCIENCE

IN

ELECTRICAL ENGINEERING

Approved

-L~~ / , /, C~n of the Committee

It

hool

August, 2000

ACKNOWLEGMENTS

I would like to express my appreciation to Dr. Thomas Trost for his kindness and

patient guidance on my thesis work. I also say thank you to Dr. David Mehrl and Dr.

Thomas Krile for helping me during the research as my graduate committee members.

11

TABLE OF CONTENTS

ACKNOWLEDGMENTS .......................................................................... II

LIST OF TABLES ... .... . ........................................ ................................... V

LIST OF FIGURES .................................................. . . . ............................ VI

CHAPTER

1. INTRODUCTION - THE TxDOT RFI PROJECT .................................. 1

n. LABORATORY TEST SYSTEM .................................................. . .. 5

Noise sources in vehicles .................................................................... 5

Laboratory bench-top tests ................................................................. 6

Test equipment. ........................... ............................................ .. .... 12

Ill. BENCH TOP TEST RESULTS ..... . .... · ..... . ..................... .. ............... 15

Broad-band noise in vehicles ................... . .. ....................................... 15

HV AC fan noise . ..................... . ............................................ ... ..... 15

SINAD test for the HV AC fan noise .................................................... 19

Fuel pump noise ........................................................................ . ... 19

Spark-ignition noise in gasoline engines ................................................ 22

Light bar noise ................................ . ............................................. 29

Narrow-band noise in vehicles ...... . ............................. . ...................... 30

SINAD test for the spark-ignition noise ................................ .. .............. 30

FM signaL ............ .. ..................... .. ................... .. ......................... 30

SAE J551/4 test and TxDOT Tex-899-B test.. .............................. .. . ... ..... 31

Multiple noise sources (HVAC fan and CW) ...................... . . .. ................ 31

iii

Multiple noise sources (HV AC fan and fuel pump) .................................... 34

Multiple noise sources (HV AC fan and spark ignition) ............................. .35

Multiple noise sources (HV AC fan, spark ignition and CW noise) ................ .37

Noise blankers in TxDOT radios ........... ... ............... ... ......................... 39

IV. TESTS ON TxDOT TRUCKS .... ............................. ... ................... .45

TxDOT vehicles .......................... .. ................................ . ................ 45

Antennas ..................................................................................... 48

SAE 1551/4 test results .......... .. ........................................................ 50

TxDOT Tex-899-B test results ............. .. ............................................. 57

Truck test summary ........................................................................ 59

V. CONCLUSIONS ... . .................................. . ................................ 61

Limit for narrow-band noise .... .............................. . ................ .. ......... 61

Limit for broad-band noise ........ ... .............. ... ............... . ..... . .............. 61

Modified SAE 155114 test ................................................................. 64

Future work ..................... .. ................................. .. ....................... 65

REFERENCES ...... . ... ...... ............................... . ...................................... 67

APPENDICES

A. TxDOT Tex-899-B TEST ....... . . . ......................................................... 68

B. SAE 155114 TEST ...... ..... . ............................ .. ..... .... ......... ... ... . ... . .... 75

C. LIST OF FREQUENCIES USED BY TxDOT .......................... . ............... 88

jv

LIST OF TABLES

1. EM! receiver and spectrum analyzer specifications .................................. .11

2. Brand, model and usage of principal equipment.. ................................... .. 14

3. HV AC fan noise peak amplitude reading from three different receivers ............ 19

4. Light bar and beacon light noise amplitudes .......................................... .29

5. Comparison of peak noise amplitudes for HV AC fan, fuel pump, and HV AC fan plus fuel pump ............. ..... .. . ... . .............................. . .... .. .. 34

6. Laboratory test of noise blanker performance of TxDOT radios .................... 39

7. Noise peak amplitude vs. noise pulse width (12 dB SINAD) ............. . . ..... .... . .42

8. Receiver sensitivity and ambient noise level (SAE test setup) ................. .. ... .45

9. Receiver sensitivity and ambient noise level (TxDOT test setup) ....... . ........... .46

10. Mode number and frequency of the TxDOT radios ............................. . . .... . .48

11. SAE J551/4 test results for TxDOT truck 2-5643-G .................................. 51

12. SAE J551/4 test results for TxDOT truck 2-5649-G .............................. .... 52

13. Peak and average value comparison of key-on noise (2-5643-G) ................... 55

14. TxDOT Tex-899-B test results for TxDOT truck 2-5643-G ........................ .. 57

15. TxDOT Tex-899-B test results for TxDOT truck 2-5649-G ............ . .. ... .. ...... 58

16. Modified SAE J55114 test procedure ..................................................... 65

v

LIST OF FIGURES

1. Simplified circuit of a spark ignition system in a gasoline engine vehicle ............... 7

2. Block diagram of laboratory testing setup ..................................................... 9

3. Directional couplers ............................................................................ 13

4. Sample wavefonn of noise from HV AC fan .............................. , ................. 16

5. 1000 data points of fan noise peak amplitude ............................................... 17

6. Probability density function of fan noise peak amplitude ................................. 18

7. Probability density function of AutoZone™ fuel pwnp noise peak amplitude ......... 20

8. Probability density function of Dodge fuel pwnp noise peak amplitude ................ 21

9. Probability density functions of three DC motors .......................................... 22

10. Simulated spark-ignition noise in gasoline engine vehicle ................................. 23

11. Rectangular pulse ............................................................................... 24

12. Periodic rectangular pulse ...................................................................... 24

l3. Fourier transform of periodic rectangular pulse ............................................ 26

14. Periodic double rectangular pulse ............................................................. 26

15. Spectrum of periodic double rectangular pulse ............................................. 28

16. SAE J55114 test values for the two radios primarily used by TxDOT .................. 33

17. Fan and spark-ignition noise for 12 dB SINAD ............................................ 36

18. Fan and CW noise for 12 dB SINAD with specific ignition noise present. ............ 38

19. Length of blanking pulse vs. frequency of noise pulse for MaraTrac radio ........... .40

20. Noise blanker performance of GE RANGR TM radio ...................................... .41

vi

21. Noise pulses and blanking pulses of Motorola MaraTrac ... ............. .. ... . .......... .43

22. Noise pulses and blanking pulses ofGE RANGR™ ......... . ........ . ................... 43

23. SWR of the antenna on TxDOT truck 2-5643-G .......................................... .49

24. SlI log magnitude of the antenna on TxDOT truck 2-5643-G ............................. 50

25. Frequency scan of module noise and ambient noise ................................... . .... 54

26. Noise from module (key-on noise) ....................................................... ... . 56

27. Modified SAE 155114 limits and TxDOT Tex-899-B limit for combination of CW and HV AC fan noise using Motorola MaraTrac Radio .... . ........... . . . .. . ... .. ... 62

Vll

CHAPTER I

INTRODUCTION - THE TxDOT RFI PROJECT

Back in the 1930s some engmeers recognized that RFI (radio frequency

interference) could be a nuisance. After years, with advancing technology, it turned into

an even greater problem especially with the advent of high-tech conununications systems

and microprocessor-based control systems. Recognition of the problem led many

engineers to become involved in EMC (electromagnetic compatibility) and as a result

several test standards, including some for automotive EMC testing, have been made.

In 1957, the SAE (Society of Automotive Engineers) already decided to set up

EMI (electromagnetic interference) standards for measuring as well as controlling RFI

[1]. The current standard for EMI was adopted in 1961 and is known as J551. This

version of test includes not just the test method and limits for broadband radiation, which

was included in the first version, but also new test methods for measuring immunity of

the vehicle to strong RF fields [2].

In the early 1980s, microprocessors and their associated circuitry became small

and inexpensive enough so many vehicle manufacturers could use them to control many

functions and add more complicated functions, which provided more convenience for

drivers. Nowadays, these ECMs (electronic control modules) are standard in most cars.

However, the clock oscillators in microprocessors, and the digital square wave signals

used in the circuitry for ·processing and control in modern vehicles are rich in harmonics,

and they are the main sources of narrow-band noise.

During the 1980s, the FCe (Federal Communication Commission) specified the

amount of interference that can be generated by a motor vehicle [3]. Thus, auto

manufacturer EMC experts worked to deal with testing and design issues, assuring

compliance with the federal regulations. These regulations are adequate to protect other

broadcasting radio services, such as TV, AM and FM radio reception in nearby homes,

but they are not intended to protect against interference to radio transceivers installed in

the vehicles. Thus the industry has had to devise an additional standard, which is part 4 of

the SAE 1551 [4] (see Appendix B). The SAE 1551/4 has been hannonized with CISPR

25 [5].

SAE 1551 has undergone modifications, and nine of the fifteen parts of SAE

1551 are now in use by the major vehicle manufacturers in the US, including GM,

DaimlerChrysler and Ford. (The other six parts are reserved for future use)

SAE is not the only US group involved in the automotive EMI problem. The

Texas Department of Transportation (TxDOT) developed its own test standard called

Tex-899-B to assure that the 800 or so new vehicles purchased every year work correctly

with their installed two-way radios. TxDOT two-way communication systems are an

essential part of the TxDOT vehicle fleet for conducting daily business. The Tex-899-B

test has recently been revised and renamed as Tex-1160-T (see Appendix A).

There are two types of EMC problems in vehicles: one is the emissions (radiation)

problem, in which the vehicle disturbs some communications equipment, and the other

one is the immunity probiem, in which some communications equipment disturbs the

vehicle. Our project is related to the emissions problem.

2

In the first type of EMC problem a certain amount of radiation from the vehicle

gets into the communication equipment as noise. This has occurred in TxDOT vehicles

that have two-way radios installed. In the worst case, the noise radiated from a vehicle

has been large enough that communication with other vehicles was almost impossible.

The TxDOT test, Tex-899-B, can identify such vehicles, but this test is not used by the

automakers. The purpose of the TxDOT RPI project is to modify the SAE J55114 test, so

as to make it correlate with Tex-899-B, in the hope that the auto makers will then use this

modified SAE J55114 test to qualify their vehicles for TxDOT service and thus reduce

TxDOT's RPI problem.

Two graduate students worked on this project previously [6,7]. They concentrated

on the effect of single-noise-source emissions. The objectives of the current thesis were

selected to complement the two former graduate students' work. They are as follows.

First, to measure the TxDOT radio response to multiple noise sources. To add to

the two former students' work, we studied the effect of two or three combined noise

sources. Chapter In of this thesis contains the results.

Second, to perform a statistical characterization of DC motor noise. The random

properties of DC motor noise make it hard to measure exact values. Chapter In includes

the statistical analysis of this random noise from an HV AC fan and fuel pumps.

Third, to carry out a simplified spectral analysis calculation of spark ignition

noise. This noise is somewhat less random than DC motor noise, so we could calculate

the frequency domain pattern and compare this with what we read from a spectrum

3

analyzer. Chapter III contains the mathematical solution of the spectrum of the spark

ignition noise.

Fourth, to determine TxDOT radio noise blanker parameters. There is a noise

blanker installed in all TxDOT radios. Since the Tex-899-B test is performed while the

noise blanker is switched on, we needed to specifY the noise blanker parameters. This is

described in Chapter Ill.

Fifth, to introduce new SAE J551/4 test limits for use with TxDOT vehicles. By

means of our data we could evaluate and compare the two main EMC tests, Tex-899-B

and J551/4, and decide on the new limits, which could improve the correlation of these

two tests.

Sixth, to validate the new SAE J551/4 test limits through whole vehicle tests. We

tested two pickup trucks used by TxDOT.

4

Noise sources in vehicles

CHAPTERII

LABORATORY TEST SYSTEM

Electromagnetic noise is produced by many parts of a motor vehicle such as the

ignition system, battery charging circuitry, accessory motors, fuel pump, airbag system,

microprocessors, starter motor, etc. Most of the above are impulsive sources, with the

ignition system being the most intense. Besides the spark ignition noise, there are two

other major noise contributors in modem vehicles. One is DC motors (also impulsive)

such as the HV AC (heater ventilation air conditioner) fan, radiator fan, wiper and fuel

pump. These are significant enough to generate some noise in on-board communication

systems. The other major noise source is microprocessors and their associated digital

circuitry. Since digital systems use relatively high frequencies and the switching action

results in even higher frequencies, the noise from digital systems may cover a broad

frequency range, including the TxDOT two-way radio band. Such noise is called narrow­

band noise, since it appears at discrete frequencies (or very narrow frequency ranges). If

the frequency components of the noise are truly discrete, they are referred to as CW

(continuous wave). Narrow-band noise can be distinguished from broad-band noise,

which has a wide, continuous frequency distribution like white noise. DC motor noise

and ignition noise can be defined as broad-band noise.

5

Laboratory bench-top tests

The bench-top tests of the TxDOT project were conducted by simulating these

three major noises in the Electrical Engineering Department at Texas Tech University. A

main purpose of this simulation was to compare the two test methods, J551/4 and Tex-

899-B, and find a modified new limit for the J55114 test to make it as effective as Tex-

899-B.

Spark ignition noise has a periodic waveform. When the breaker points open,

there are two sparks and thus two noise pulses. One occurs at the distributor and the other

at the spark plug. As the engine runs, the two pulses are repeated periodically. The

simplified circuit is shown in Figure 1 [8]. In the upper diagram, the points are closed and

the inductor, labeled TX, is charging. In the lower diagram, the points have opened,

producing the high inductor voltage and the resulting sparks. (Nowadays, a transistor is

used instead of breaker points.)

The spark ignition noise was simulated by an EH pulse generator. Since the

antenna circuit works as a VHF band-pass filter, the pulse captured at the antenna has a

ringing characteristic. Thus a band-pass filter was used at the output of the EH pulse

generator to simulate the antenna ringing.

In order to simulate the HVAC fan noise, a Dodge fan was run alone with a 12 V

battery. The battery and fan were put inside a metal chamber to isolate the fan noise from

ambient noise in the laboratory. The metal chamber was also used for other DC-motor

noise sources such as an AutoZone TM fuel pump and a Dodge fuel pump. These

impulsive noises were captured by a current transformer (FCC F-33-1 current probe).

6

'.

'.

. P1''--

.. P2+- .

. 'diStiib'ufoi .

. 'C.

P~

. P5e-

. . .

.. pr.-- ...

Figure 1. Simplified circuit of a spark ignition system in a gasoline engine vehicle

7

Noise from micro-controllers and their associated circuits is mainly divided into

two types of signal. One is a CW signal and the other is an HMCW (heavily modulated

continuous wave) signal. Simulation of the CW signal was done with our Rohde &

Schwarz radio communication service monitor by setting it to a fixed frequency.

Simulation of HMCW was conducted previously by Jin [6] but was not used for the

present work. The detail block diagram of the test set up is shown in Figure 2.

A Fluke FM signal generator is used to simulate a received 1.0 IlV FM

communication signal at the antenna. A 1.0 kHz audio modulation frequency and 3.3 kHz

frequency deviation were used for this signal. Two types of directional couplers allow

this FM signal to combine with one, two or three noise sources. The combined noisy

signal is delivered to the EMI receiver and TxDOT radio receiver through a coaxial

cable. The reading from the CISPR-compliant EMI receiver (Rohde & Schwarz model

ESS) represents the SAE 155114 test [9].

The audio output of the TxDOT radio was connected to a SINAD meter through a

load and transformer. The audio volume of the radio was adjusted for 1.0 W audio output

power. HP 8903 A and B audio ana1yzers were used to measure SINAD (signal noise and

distortion) values from the output of the radio. Measuring the SINAD value from the

audio signal output of the radio is the procedure used for the Tex-899-B test. The SINAD

value is defined as shown below [10].

SINAD( dB) = 2010 [rms value of signal, noise and distortion (VoltS)] glo rms value of noise and distortion (volts)

8

R&SRadio Comm. (C\\(noise)

3

EH pulse gen. (I~itioItnQise)

Fluke signal gen. (FM signal)

D Oscill-oscooe

Current Probe

o EMl Receiver

. __ ._ .. __ ......... ,,.~ ....... Directional

2

couplers

3

4

Band-pass Filter

2 3

4

Attenuator

TxOOT Radio

D Oscill­oscooe

Audio Load

Resistor

Audio analyzer. (sJN~ meter)

Figure 2. Block diagram oflaboratory testing setup

9

Audio Trans­fonner

Instead of measuring the amplitude of the signal and the noise from the audio

output of the radio, the SAE J551/4 test measures the amplitude of the noise directly at

the antenna. So, the SAE J55114 test results appear with units other than dB. The most

common units are dBJ.1V and dBm. The dBJ.tV is the unit defining the amplitude of a

signal compared to 1 Jl V> that is

dBpV = 20 10g1o [amPlitude in PV]. IpV

The dBm is the unit relating the power of the signal to I mW, that is

dBm = dBm W = 10 10glo[amplitude in m W]. ImW

These two units are very popular in communication system engineering. If it is a 50 n

system, the relation of these two units can be found as follows:

= 10 log\O(lxl0-6xlxl0-6xlO+3/50) dBm = -106.98 dBm.

Nine radios were supplied for the project by TxDOT radio shops in Austin and

Lubbock. We used only four radios in the present study since these four are the ones

mainly used by TxDOT. Four sensitive instruments have been used to measure the RP

output level of the noise sources. The specifications of these instruments are mentioned in

Table 1.

10

£ sa ....

Table 1. EMI receiver and spectrum analyzer specifications (Internal noise level and dynamic range)

ROHDE & SCHWARZ ESS EMI RECEIVER (dBJlV)

IFBW 120 kHz (pre-amp on, 25 measurement time) 10kHz (pre-amp on, 25 measurement time)

Detector PK QP PkIM AV RMS PK QP PkIM AV RMS

10 dB atten* 11.5- 5.9- 29.2- -0.4- 0.3- -0.4-

6.1 39.6- -11.4-

-10.6 13.4 6.0 30.4 -0.6 0.4 1.1 41.8 -11.5

o dB atten* 1.5- - 4.0- 19.3-

-10.4 -9.6 -8.3- -3.9- 30.4- -21.5-

-20.7 2.8 -3.9 21.1 -10.5 I -4.0 32.1 -21.4

Dynamic range: up to 137 dBIlV (when RF attenuation ~ to dB) Dynamic range Operating range: 60 dB

Typical noise figure: 8 dB with preamplifier, 12 dB without preamplifier

ROHDE & SCHWARZ ESVP EMI RECEIVER (dBJlV)

IFBW 120 kHz (pre amp on, 28 measurement time) 10kHz (pre amp on, 25 measurement

time)

Detector AV Pk CISPR MIL AV Pk MIL

10 dB atten* -2.6 10.5 - 9.8 1.4 30.3 - 29.2 -6.0 -0.3 - -1.9 41.4-39.2

o dB atten* -12.6 l.l - -0.2 -8.6 20.3 - 19.4 -16.0 -9.9 - -I 1.5 31.0 - 29.6

Dynamic Dynamic range: up to 137 dBIlV (when RF attenuation ~ 10 dB) Operating range: 60 dB

range Typical noise figure: 6-8 dB with preamplifier, 14 -16 dB without preamplifier,

SCHAFFNER SCR 3101 EMI RECEIVER (dBJlV)

IFBW 120 kHz (2s measurement time) 9 kHz (2s measurement time)

Detector PK AVLD QPcisp PK AVLD

to dB atten* 16.4-17.5 5.5 -0.6 - -0.5 *** 2.7

o dB atten* 7.3 - 8.2 -4.5 -10.6--10.5 -6.2--7.8 -7.3

Dynamic range: - 23 - + 130 dBI.N. Dynamic range (In QP detection mode with no autoranging activated, it is 7 dB.)

(Accuracy better than 1.5 dB in temperature range + 15 ... +35 deg. Celsius. )

HEWLETT PACKARD 8592L SPECTRUM ANAL YZER

D"~ PK (sweep time: 2 sec) Video A V (100 sweeps: 2 sec for each)

RF Atte OdB I lOdB OdB I 10 dB Level 21dBJ.1V I 31dBJ.1V 9 dBIlV I 19 dBJ.1V

Optimum dynamic range (77 dB)

Dynamic range Amplitude Range (-130 dBm to 30 dBrn) Resolution Bandwidth (30 Hz to 3 MHz) Operaring frequency range (9 kHz to 22 GHz)

Atten* : RF attenuation

11

*** : not available Each of the three receivers was available to us during a different period of time.

The ESS receiver from Rohde & Schwarz is a newer model than the ESVP receiver. They

have the same dynamic range but the ESS has additional automatic data-taking features.

The Schaffner receiver has less sensitivity than the two receivers from Rohde & Schwarz,

but it is very portable and good enough to measure broad-band noise. The HP 8592L

spectrum analyzer is not good for measuring accurate noise values but is good enough to

see the frequency domain characteristics of the noise.

Test equipment

A large array of equipment has been used for the bench-top tests. Three different

pulse generators have been used to simulate spark ignition noise. Two RF receivers and

two spectrum analyzers have been used to measure the amplitude of the noise. In addition

multiple SINAD meters and oscilloscopes were used. Table 2 gives detailed

specifications of the test equipment.

Two hybrid junctions and a 3-port directional coupler have been used to combine

the signal with three noise sources. For the 4-port hybrid junctions, there is 3.6 dB loss

from input to output and either 00 or 1800 of phase shift. The 3-port directional coupler

has two inputs and one output and each path has a different coupling loss. Port 3 to port 1

has 0.5 dB loss and port 2 to port 1 has 20 dB loss. Figure 3 shows the coupling paths of

the couplers.

12

3 1

2

Hybrid Junction 3-port Directional Coupler

Figure 3. Directional couplers

13

Table 2. Brand, model and usage of principal equipment

Category Brand and model Usage

Rohde & Schwarz ESS EMI receiver I

Rohde & Schwarz ESVP EMI receiver

RF recelvmg Schaffner SCR 3101 EM! receiver Noise amplitude measurement

equipment in frequency domain HP 8592L spectrum analyzer

HP E7401A EMC analyzer

SINAD HP 8903 A and B audio analyzers SINAD (dB) measurement meter

HP 54616B, 2 Gsals, 500 MHz Visualize

Oscilloscope HP 54602B, 150 MHz time domain waveform

Fluke PM 3370A, 1 MSals, 60 MHz Audio frequency waveform

EH Research Labs 139B pulse generator

Tektronix 110 pulse generator Spark ignition noise simulation

Signal HP 222A pulse generator generator

Fluke 6060B RF signal generator FM signal generation

Rohde & Schwarz CMS 54 radio CW noise simulation

communication service monitor

Midland stereo amplifier Audio signal amplification

Amplifier Mini circuits ZFL-500 HLN low noise pre-RF signal amplification

amp

Network HP 8753C

Impedance check for the analyzer directional coupler Current FCC F-33-1 current probe Capture the current waveform transformer

HP 8494B attenuator Used to decrease the amplitude Attenuator Weinschel3200T-l programmable of DC motor noise and spark

attenuator ignition noise

Directional Synergy Microwave DJK-702N 9650, Couple multiple devices

coupler DJK-702N 9723 and DJK-702S 9615

Band-pass Custom made Simulate antenna ringing

filter

14

CHAPTER III

BENCH~ TOP TEST RESULTS

Broad-band noise in vehicles

Broad-band disturbance emissions are mostly caused by DC motors and spark

ignition systems. We simulated three types of DC-motor noise sources: HV AC fan, fuel

pump and radiator fan. We used actual DC motors taken from vehicles for these

simulations. For the spark ignition noise simulation, we used an EH Research Labs 139B

pulse generator. We measured the peak amplitude of this broad-band noise with the use

of 120 kRz bandwidth. (The bandwidth for the measuring equipment is specified in the

SAE J551/4 test. See Table 3 in Appendix B.)

RV AC fan noise

A Dodge HV AC fan and a Dodge radiator fan were used in this bench-top test.

The fans were put inside the metal chamber while we measured the noise level. Only the

HV AC fan was found to be noisy; the radiator fan was extremely quiet. The reason why

the radiator fan has low noise, even though it has two DC motors, is that it has filters

installed at the back of the motors. No further use was made of the radiator fan in our

tests.

Because of the inherent random property of fan noise, we cannot give the exact

waveform of the noise. Al~lOugh it has a large quasi-periodic peak about every 1700 JlS,.

15

the peak value and the period are not stable. Figure 4 is one sample of the HV AC fan DC

motor noise waveform captured by the HP 54616B oscilloscope.

Hf54E! 5e C1fd-: Re,,) fL ~2. ;.(3 16:4S:J7 Wad ~ar 2~, 2000 1_.JL5~C~ 1G2/5 re>. O~, 1 .oor~,,r _,J:t_§10E.,

j"

Figure 4. Sample waveform of noise from HV AC fan

The random property of the fan noise suggested that a statistical analysis was

needed. and a test was performed using a computer program. The HV AC fan was run by

battery inside the metal chamber. A current probe was connected to the R & S ESS EMI

receiver to measure the peak amplitude of the fan noise. The ESS receiver was connected

to a computer through IEEE cable, and 1000 data points offan noise peak amplitude were

captured by a LabView program. The captured 1000 data points are shown in Figure 5. It

16

takes 2 seconds of measurement time to get each point. Horizontal and vertical axes of

the figure indicate time in seconds and amplitude of the RV AC fan noise in dBJ.1V,

respectively. We used peak detection at a frequency of 47.02 MHz with 120 kHz

bandwidth for this measurement. The speed of our fan is about 2700 rpm at 13 volts. A

Stroboscope was used to measure the speed.

0 « >54 J:

52

50

48 0 200

Fan ndse peak values(rrean=53.78 dBW , sld=2.29 dB)

... ... ... ... ...

... ...

... ...

......

400 600 800 1(0) 1200 1400 1600 tirre [seccn:I]

Figure 5. 1000 data points of fan noise peak amplitude (2 s measurement time, 120 kHz BW)

17

...

.. ..

1800 2000

The average of these 1000 data points of RV AC fan noise power was 53.78

dBJ.1V, and the standard deviation was 2.29 dB. Perhaps the first hundred data points do

not exactly represent fan noise because this portion of the data is decreasing while the

later part is relatively stable. The decreasing may be just an initial transient effect, so we

looked at the last four hundred values only. For these the mean value of the fan noise

peak amplitude is 53.89 dBJ.1V, and the standard deviation is 2.04 dB.

0.16r----r----~--~----~----~--~----~---.,---~

c: o U

0.14

0.12

§ 0.1 -~ 'jjj

ID 0.08 -a ~ ~ 0.06 .0

e a.. 0.04

0.02

O~--~----~--~----~----L----i----~~~~--~

48 50 52 54 56 58 60 62 64 Power of fan noise (dBIN)

Figure 6. Probability density function of fan noise peak amplitude (Mean: 53.78 dBJ.1V, std dev : 2.29 dB)

18

66

Figure 6 shows the probability density function of these 1000 data points. From

the figure you can see that most of the data are located between about 52 and 56 dBI-lV.

Hence, we can say fan noise has random behavior, but it is fluctuating within a ± 2 dBI-lV

range of its average value.

SlNAD test for the HV AC fan noise

The bench-top setup shown in figure 2 allows us to measure the peak amplitude

value of one or more noise sources while a signal with the noise produces a 12 dB

SlNAD reading. We adjusted the fan noise attenuation to make 12 dB SlNAD, and we

read the peak amplitude of the fan noise. Each EMI receiver read slightly differently,

however they showed good agreement. Table 3 gives us a brief comparison of the fan

noise peak value readings of the three different receivers. A Motorola MaraTrac radio

was used for these tests.

Table 3. HV AC fan noise peak amplitude reading from three different receivers (for 12 dB SINAD)

Rohde & Schwarz Rohde & Schwarz Schaffher ESS receiver ESVP receiver SCR 3101 receiver

50 - 55 dBJ.! V 48 - 53 dBJ.!V 43 - 58 dBJ.! V

Fuel pump noise

Fuel pumps can make as much broad-band noise as fans. We employed two fuel

pumps for simulation purposes. One is used on Dodge trucks and the other is made by

19

AutoZone™ and used on GM trucks. The fuel pumps were mounted in metal containers

filled with Stoddard solvent. The pressure of the pumping is measured during every test.

The usual setting of pressure was 49.22 psi, which is the setting used on Dodge trucks.

For the AutoZone™ fuel pump we set the pressure at 10.5 psi.

Like fan noise, fuel pump noise is random. Hence, We have done the same

statistical analysis. Figures 7 and 8 show the probability density functions of fuel pump

noise peak amplitude for the two pumps.

0.18r---~r---~----~----~----~-----r----~----~

0.16

0.14

c: g 0.12 o c: .2 2:' 0.1 '0 c: Q) i 0.08

:0 ~ 0.06 e Q.

0.04

0.02

O~~~~--~----~----~----~---=~-----L~--~ 34 36 38 40 42 44 46 48 50

Power of fuel pump noise (dBIlV)

Figure 7. Probability density function of AutoZone™ fuel pump noise peak amplitude (Mean: 39.93 dB~V, std dev : 1.58 dB)

20

The AutoZone™ pump makes less noise than the Dodge pump by 15 dB, and the

Dodge pump has a bigger standard deviation. From the figures, you can see that the fan

noise has a wider distribution than the AutoZone™ fuel pump but narrower than the

Dodge fuel pump, and the mean value of the fan noise is more like the Dodge fuel pump

than the AutoZone™ fuel pump. A comparison of probability density functions of these

three DC motor noise sources is plotted in Figure 9.

The Dodge fuel pump noise peak amplitude for 12 dB SINAD turned out to be

around 44 dBJlV. The Motorola MaraTrac radio was used for the measurement. The

measurement time and bandwidth were 2 sand 120 kRz, respectively.

0.16~---T----~----~--~----~----r----T----~--~

c: o

0.14

0.12

n .2 0.1 >­:t: III 5i 0.08 -0

£: :is 0.06 (!! .c e Cl. 0.04

0.02

52 54 56 58 60 62 64 66 68 Power of fuel pump noise (dBrN)

Figure 8. Probability density function of Dodge fuel pump noise peak amplitude (Mean: 56.31 dBJlV, std dev: 3.27 dB)

21

0.18

0.16

0.14

0.12 >.

:t:!

.0 0.1 m .0 0

0.08 l-

Q.

0.06

0.04

0.02

0 -8 -6 -4 -2

. . . _---', . ; ; L _____ ; ,

0.._- ...... ,:

o 2

· · · · · · · · · '--------LL_

4 6 Peak amplitude relative to mean (dB)

i ... · ....... 1 ... _ ........

j

8 10 12

Figure 9. Probability density functions of three DC motors

( -- : HV AC fan, _._ .. : Dodge fuel pump, ----- :AutoZone™ fuel pump)

Spark-ignition noise in gasoline engines

The next broad-band noise source is spark ignition. Figure 1 in chapter I shows

the spark ignition system in a gasoline engine vehicle. The period of the spark ignition

pulses can be derived from the engine speed. If a 6-cylinder engine is used and the speed

at idle is 1000 rpm, there are six spark pulses in each turn of the crankshaft, that is, 6000

pulses in a minute, and thus 100 pulses in a second. Therefore, the period of the pulses is

10 ms. Assuming the ignition system has a distributor, sparks occur there in addition to at

22

the spark plug. The interval between pulses from distributor and spark plug was measured

from a vehicle as 10 J-ls. We set the pulse width as 10 ns, and the ringing pattern caused

by the antenna circuit was simulated by use of a band-pass filter. The simulated pulse of

spark ignition noise is captured by the HP 5416 B oscilloscope and shown in figure 10.

H~S46rS8 1 .~

Code Rev Ih~2.30 ·ZG~

16141=24 Ued "~r 2B, 2000 .... ·.OCE. S().O / Pk ~ UN

lOms.

•• - > ., ~.'

, , : ........ ~ .... ~ ~ • ~ • - • " ~. ~ ; • j >. I •• ~ ~

Figure 10. Simulated spark-ignition noise in gasoline engine vehicle (one pulse)

We set the pulse width as IOns, second pulse delay as 10 J-lS and pulse period as

23

XI{t)

A .--+--.

.. .... -0.5 0.5 time{l0·8s)

Figure 11. Rectangular pulse

Assuming for simplicity simple rectangular pulses, rather than the ringing pulses

of Figure 10, we can easily calculate the Fourier transform. To begin let us consider one

rectangular pulse itself (see Figure 11). The Fourier transfonn of a rectangular pulse is a

sinc function as shown below.

= A sin(Jif) = Asinc(f) '!if

v A ......

-0.5 0.5

...... i /i

t -0.5 a

where ()) = 2'!if

t +0.5 a 2t -0.5 a 2t +0.5 a

Figure 12. Periodic rectangular pulse

24

.. .... ( -8 s) time 10

If the rectangular pulse is periodic, as shown in Figure 12, the Fourier transform

needs to be modified as shown below.

ro 0.5 ±(l. +0.5) ±(21. +0.5)

X2(w)=F(x2 (t))== jx2 (t)e-Jilt dt==A[ je-Jiltdt+ je-Jiltdt+ je-J~dt+ ... ]

-<t> -0.5 ±(t.-0.5) ±(2t.-0.5)

<t> 2nk T ro .

( by using of the Poisson formula L o(w--) =- LeJnmT ) [11]

k .. -«> T 21r n=--«>

1 '" 1 == Asinc(f)- Lo(f n-)

IQ n=--«> IQ where k,n is integer.

The resulting Fourier transform of the single periodic rectangular pulse is shown

in Figure 13. This corresponds to a distributorless ignition system. As you can see in the

figure, the spectrum is formed of consecutive delta functions, which follow the envelope

of the sinc function. Each delta function is separated by 100 Hz, so figure 13 is

exaggerated to show the delta function and sinc function together. [12]

25

100A

00 100 200 300

Frequency (MHz)

Figure 13. Fourier transfonn of periodic rectangular pulse (not to scale)

'" ..... 1 ..... .....l ......

f ..... 1

A -r- r-- r+-

I ! ........... '" ........ !

, ! .. -0.5 0.5 tb-0.5 tb+0.5 II\ta+0.5 1 \ ta+~+0.5 time(I'(r

t ll-0.5 ta+tb-0.5

Figure 14. Periodic double rectangular pulse

26

Figure 14 shows the periodic rectangular pulse waveform, which corresponds to

an ignition system with distributor. The Fourier transform is calculated below:

'" X 3(m) = F(X3(t» = Jx3 (t)e- Jat dt

0.5 ±(I. w.S) ±(I. w.5) ±(" +1. +0.5)

= A Je-Jat dt + A Je- jdJf dt + A Je-Jaw dt + A Je- jaw dt + ...

-0..5 ±(I.--O.5) ±(I.--O.5) ±(1.+1.-0.5)

= X 2 «(j) + e-jat• X 2 «(j) = X 2 «(j)(1 + e- jat. ) ::::: X 2 «(j)(l + COS(]){h - j sin (]){ h)

1 GO I = Ag( (]){ h )sinc(f) - I 5(f - n -)

t b 11=--<0 t a

The resulting graph is shown in Figure 15. The consecutive delta functions have

an envelope given by the function g( (j) tb). Again, this graph is exaggerated to show every

function in one picture. Actually, g( (j) tb) has 1000 peaks in each lobe of the sine function,

and each lobe of g( (j) tb) contains 1000 delta functions.

27

".-... ..... '-" 100Hz <"l

>< -0

E '-0 -(Jl c ca .... -.... IV .L: ::J 0 u.. 100MHz -0 IV

'"0 100kHz

::J ~ C Cl

---'1 i~ ca :2

Frequency (MHz)

Figure 15. Spectrum of periodic double rectangular pulse (not to scale)

Somebody might ask whether we really need 120 kHz bandwidth for ignition

noise amplitude measurement rather than 9 kHz bandwidth, which is used for narrow-

band noise. The answer is definite. In a practical situation, there is always some jitter in

the spectrum and in doing a peak amplitude measurement for an EMC test, you'd like to

be able to make a single, accurate measurement. Using the 9 kHz bandwidth gives only a

portion of a lobe of the 100 kHz periodic envelope, while using 120 kHz bandwidth gives

an entire lobe. In view of the jitter, the 120 kHz bandwidth is preferred because the

readings do not change from one measurement to the next. We verified this by

28

experiments. We could get a stable peak value of the ignition noise with 120 kHz

bandwidth, while we got an unstable peak value for 9 kHz bandwidth.

Light bar noise

Light bars do not come with new vehicles but are installed by TxDOT. The

colored lights on the bars are used to provide warnings to motorists. The bars use tiny DC

motors to rotate reflectors behind the lights. These motors are the noise sources in light

bars.

We tested a light bar and two beacon lights at the lab. The beacon lights have a

single flashing bulb and no motor. The light bar that we tested has four motors in it with

filters installed on all motors. Three capacitors soldered at the back of each motor

constitute the filter. We tested the light bar with and without the filters installed. The

table shown below gives the data for the light bar and beacon lights (Table 4).

Table 4. Light bar and beacon light noise amplitudes

DBJlV Light bar Light bar Beacon light 1* Beacon light II** With filter Without filter

Peak 7.6-14.1 29-37 42-47 62-65

amplitude

* : blinking light

** : blinking light with audible tone

From the table we found the light bar noise is not sufficiently high (not above the

40 dBJlV limit) to fail the Tex-899-B test either with or without filters installed. We

29

couldn't even reduce the SINAD value below 28 dB with this light bar. The two beacon

lights have much higher peak amplitudes but just make 24 dB SINAD because their pulse

rate is extremely low, on the order of a second. The measurement was made at 47.02

MHz with 120 kHz bandwidth, and the measurement time was 2 s. The ESVP receiver

was used.

Narrow-band noise in vehicles

CW RF noise typically comes from harmonics of the oscillator used in digital

circuitry. A sine wave without modulation at the same frequency that is used in the

TxDOT radio under test was generated by the R & S CMS54 radio communication

service monitor for the CW noise simulation. Since we were using a pure sine wave, it

would measure the same with an average detector as with a peak detector. This type of

noise is narrow-band and it can be measured at 9 kHz bandwidth rather than 120 kHz.

SINAD test for the spark-ignition noise

We were not able to reduce the SINAD value by increasing the peak amplitude of

spark ignition noise. Since the noise blanker in the radios works very well for the ignition

noise, even at the maximum output of the ignition noise generator, which is 88 dBJlV in

120 kHz bandwidth, we couldn't make any change in the SINAD value.

FM signal

30

The FM signal is generated by a Fluke 6060B signal generator. Tex-899-B

specifies the FM signal to be set on-channel and modulated with a 1 kHz sine wave tone

at ± 3.3 kHz deviation. The maximum amplitude of the FM signal should be no more

than 1 Jl V (-107 dBm) in order to obtain a 12 dB SINAD reading. These values were

used for all the SIN AD tests in our bench-top studies.

SAE 1551/4 test and TxDOT Tex-899-B test

The Tex-899-B test specifies an RF emission limit of 12 dB SINAD at the audio

output of the TxDOT radio while a 1 Jl V FM signal is present. This is different from the

155114 test, which specifies the RF emission limit directly at the antenna without an FM

signal present.

To see the correlation between the two tests, first we send the 1 j.lV FM signal and

a selected noise to the TxDOT radio, and then adjust the noise to obtain a 12 dB SINAD.

Once we get the 12 dB SINAD, the power of the noise is measured at the radio input,

which gives the 155114 test limit corresponding to the Tex-899-B test limit.

MUltiple noise sources (RV AC fan and CW)

Instead of using only one noise source, we added two, fan and CW, to the FM

signal and then performed the SINAD test. Two directional couplers were used to

combine the noise and signal. An amplifier and attenuator were used to adjust the power

of the fan noise. First we set the fan noise value very low (0 dBj.lV) and then adjusted the

CW noise to get the total combined noisy signal to make a 12 dB SINAD. Then we

31

measured the peak amplitude of each noise at the radio input. This indicated the SAE

J551/4 test value corresponding to the TxDOT limit. Then we repeated the measurement

for gradually increased HA VC fan noise, until the fan noise reached its maximum

possible value (near 60 dB JlV). Noise amplitudes were measured at 47.02 MHz by the

Rohde & Schwarz EMI receiver with peak detection mode. The same 2 s measurement

time was used, but different measurement bandwidths were used for the two noise

sources. A 120 kHz bandwidth was used for the broad-band noise measurement, and 9

kHz bandwidth was used for the narrow-band noise measurement. The same test was

repeated three times to check repeatability, and this resulted in three curves for each

radio. There are nine radios of five different models in our laboratory, but we

concentrated on just two radios, since these two radios are the most common ones in the

TxDOT vehicle fleet. These are the GE RANGR TM and the Motorola MaraTrac. Figure

16 shows the SAE J55114 test values for the two radios when the noise is at the limit of

the Tex-899-B test. In other words, the curves in Figure 16 show the relationship of the

peak noise amplitudes which results in a 12 dB SINAD with an FM signal. As the HV AC

fan noise gets smaller, the CW noise becomes larger. The X-line indicates the current

limit of the SAE J55114 test for broad-band noise. The current limit for narrow-band

noise of the SAE J55114 test is 0 dBJlV. Hence it's not shown in this graph.

32

60~------~~--____ ~ ________ ~ ________ ~ ________ -. ________ ~

50

5' 40 :1. m :£ Q) "0 .a 13.. 30 E «

.::.! m Q) a. ~ 20 '0 z c: m u. U ~ 10 I

"'--_'\?'"'-=~:~~;;;::~==:--:==~-----.-.--... ..... -.... ..--.-9.. .. V..,

e·· __ ~~::::::==~·· __ ··_ ... _e_~~.~~:~_-Q '-...;~\ .. ~

~ ~\

rr " I x x x x x x x x x x x x x x x x ~ x x

q

O~--------~------~~------~------__ ~ ________ ~ ________ ~ ~ ~ ~ ~ ~ ~ ~

CW Noise Peak Amplitude (dB!J.V)

V : Motorola MaraTrac. o :GERANGRTM. X : Current limit used for SAE 155114 test.

Figure 16. SAE J55114 test values for the two radios primarily used by TxDOT

As you can see, the two limits, the one corresponding to Tex-899-B and the

current 1551/4 one, don't agree with each other. The current 155114 limit for broad-band

should be increased from 28 dBJlV up to 40 dBJlV (or even to 50 dBJlV if considering

only the MaraTrac) to prevent the vehicle which makes noise between 28 dBJlV and 40

33

dBJ.1V from failing J55114 while passing Tex-899-B. And for narrow-band, the limit

should be decreased to about -3 dBJ.1V to make J55114 agree with Tex-899-B. This is

reasonable, because Tex-899-B specifies that the maximum received FM signal should

not be more than 1 J.1 V (= 0 dBJ.1 V), and of course no radio can work with noise equal to

signal power.

Multiple noise sources (}IV AC fan and fuel pump)

We also performed a SIN AD test for the HV AC fan and fuel pump together. We

used the Dodge fuel pump for this test. Both of the DC motor noise sources were put

inside of the metal screen box, and the current probe was connected to the Schaffner SCR

3101 EMI receiver and Motorola MaraTrac radio by a directional coupler. An amplifier

and attenuator were connected before the directional coupler to adjust the power of the

noise from the DC motors. A 120 kHz bandwidth and 2 s measurement time were used

for this measurement. The results are shown in Table 5.

Table 5. Comparison of peak noise amplitudes for HV AC fan, fuel pump, and HV AC fan plus fuel pump

HVAC Fuel HVAC fan HVAC I Fuel

HVAC fan + + fan pump

Fuel pump fan I pump

Fuel pump

Battery voltage 12.55 12.70 12.40 12.57 12.70 12.38

SINAD (dB) 8 ~ 15.5 11~13 IO~ 14 10~ 14 1l~13 9 ~ 15

Attenuation (dB) 6 6 11 4 8 10

EMI level (dBJ.1 V) 45- 52 41-48 42-48 49- 53 40-48 40-46 (48.5)* (44.5) (45) (51) (44) (43)

Note*: average value of the peak amplItude readmgs

34

We conducted the test twice to check the repeatability of these values. We found

that the RV AC fan noise peak amplitude for 12 dB SINAD went down by about 6 dB

when we used both the fan and fuel pump simultaneously. In the previous section we

discussed our new limit of the SAE test for broad-band noise. We saw that the fan noise

peak amplitude for the 12 dB SINAD is around 48 to 55 dBJlV, but if we add fuel pump

noise, which is always present while an engine is running, this value will decrease about

6 dB. For this reason we choose the 40 dBJl Vas our new limit for broad-band noise.

Multiple noise sources (IN AC fan and spark ignition)

Instead of using fuel pump noise we added spark-ignition noise to the FM signal

with RV AC fan noise. Our simulated spark-ignition noise, generated by the EH pulse

generator, has the following specifications: double-pulse mode, 10 ns pulse width, 10 Jls

second pulse delay and 10 ms pulse period. In this particular test we connected the

ignition pulses directly with the fan noise without using the band-pass filter in order to

get more power for the ignition noise. The results are shown in Figure 17. The Motorola

MaraTrac radio was used. Figure 17 will help you to see the distribution of fan noise

peak amplitude for 12 dB SINAD at each ignition noise level. The solid line connects the

mean value at each ignition noise leveL A trend from lower left to upper right is seen in

the data in Figure 17, although it is very slight, about 5 dB in fan noise. The reason for

this trend is not known, and in fact it is not always repeatable, one test having produced

an opposite trend.

35

70r---~-----r----~---'r---~----~----~----r----'

*** ..- ** 60 - *"****t * * > ::1

co "'0 ........ • .... ** ~."* ** Q) 50 ;::s "';;,i >

.:.<: ell ** ***t:tt ** ** Q)

C Q) 40 ,~ 0 t:: t:: ..- *** 0 ,-..... '2 30 ,~

I

~ ..- ..... * * C\l c rn

20

10 ***** * 42 44 46 60

Fan noise peak value (dB/..lV)

Figure 17, Fan and spark-ignition noise for 12 dB SINAD

36

Multiple noise sources (RV AC fan, spark ignition, and CW)

A question arising in regard to figure 16 is whether the presence of spark ignition

noise, in addition to the fan noise and CW noise, would change the shape of the curves.

This is a matter for practical concern since in a gasoline-powered vehicle with the engine

running, the spark ignition noise would be present.

To investigate this situation we connected three noise sources: HVAC fan, spark

ignition, and CW, in our test setup and performed the usual 12 dB SINAD test. We used

the band-pass filter with the ignition noise, a Motorola MaraTrac as the TxDOT radio,

and three directional couplers to combine noise and signal. The results are shown in

figure 22.

Each curve in the figure corresponds to a particular value of ignition noise. If we

look at the left end of the curves, there does seem to be a trend - as the ignition noise is

increased, the fan noise must be lowered - but there is considerable random variation

also. We find this data, like the data in Figure 17, to be somewhat inconclusive as far as

the effect of ignition noise is concerned. And we do not feel justified in trying to use this

data to adjust the 40 dBJlV limit that we established on the basis of table 5.

37

.,.-...

> ::l

t:O "'0 '-" (\)

"'0 ;:::I -+-' .-0. ~ ~ (\)

A (\) U'l

'0 t::

m J:.I..

50

45

40

35

30

25

20

15

10

5

0

-5 -14 -12 -10 -8 -6 -4

CW noise peak amplitude (dBf.lV)

\J : Ignition noise = 58.6 dBf.lV

<l : Ignition noise = 54.3 dBf.lV

0: Ignition noise = 44.6 dBf.lV

*: Ignition noise 30.0 dBf.lV

0: Ignition noise = 20.2 dBf.lV

t::. : Ignition noise = 57.0 dBf.lV

t>: Ignition noise = 51.1 dBf.lV

0: Ignition noise = 36.8 dBf.lV

+: Ignition noise = 25.9 dBf.l V

*: Ignition noise = 0 dBf.l V

Figure 18. Fan and CW noise for 12 dB SINADwith speCific ignition noise present.

38

-2

Noise blankers in TxDOT radios

Noise blanker circuits are installed in the TxDOT radios. The GE RANGR™

circuit is turned on and off by connecting two jumper wires, while the Motorola

MaraTrac can be turn on and off by a switch. The noise blanker circuits in these radios

are very effective for spark ignition noise, somewhat effective against noise from DC

motors such as fuel pumps and HV AC fans, and ineffective for CW noise and thermal

noise [6].

The noise blanking circuits of the two radios work similarly but against DC-motor

noise the Motorola MaraTrac is somewhat more effective. A brief summary of the

characteristics of the noise blankers in both radios is shown in Table 6. The

characteristics were found by using an EH pulse generator as the noise input to the radio.

Table 6. Laboratory test of noise blanker performance of TxDOT radios (pulse length of noise pulses = IOns)

Blanker Characteristic Radio

MaraTrac RANGER™

Type of circuit IF detect and IF detect and IF blank IF blank

Blanking disable / enable Push button Internal jumpers

Length of blanking pulses 8 /lS 2 J.!S

Minimum amplitude of 3mV 2mV

noise pulses for blanking

Maximum amplitude of >7V >7V noist? pulses for blanking

Pulse-rate shut down 300 kpps 250 kpps

39

For the Motorola MaraTrac the length of blanking pulses depends on the

amplitude and repetition rate of the noise pulses. Figure 19 illustrates the relationship of

length of blanking pulse and noise pulse repetition rate (frequency).

8.-----------.------------r----------~------------r_----------~

B BB@B€ip B ~B~ @ ~§~ I 7 ................. ~ ............................................ ·· .. ·········· .. ················ ...... · .... ···t·········· .. ·· .. ··············· .. ··· .... ·· .. ········· .. ·i .. ·· .. ·&l···(3····· .... · ... _ ............ -....... \ ................... -_ ............................ ..

6 -------l----------~-----------:----------l-------------­i 5 ---------1------r-------t-g*---~ 4 .... ----.. - ............................ L ... - .................................. --.... L .. ~ .. -................... ~ ...... - ... -..... -l ..... --................ - ................. _ ... 1.9 ............................................. ..

~ . i I 10 ! 3 ·· .... · ....... · ........ · .. ···· .. ···· .. · .......... ·····1· .. ·_ .. ··· .. · ...... ·· ................................ 1' .............................................. · ...... ·T· .. ·· .. · .. · .... ······ .. · .. · __ ........ ·· .. · .... · .. t· .... : .... · .... · ................................ .

2 .. · ......... · .. · ........ · ...... · .... · .. · .... · ...... · .. 1-........................... ·.................... .. ......................................... + ........................................ _ .............. ~ .................................................... ..

i 0

·-··-·· .... '·· .. ·~·-.. ···---······ .. i ... ·~····· ..... -··· ... ··---········· .. -·· ... ·· .. ·r-··-···-············~····---······--···---t-· ...... ····· ...... · .. ·_··_ .. ·· ........... __ ... ---t····_··o-_···_ .. ····.....,.·· ..... -.-.. __ ...

I I I I o~----------~----------~----------~------------~~~er----~

Noise pulse frequency [Hz]

0: Measured while decreasing the frequency. 0: Measured while increasing the frequency.

Figure 19. Length of blanking pulse vs. frequency of noise pulse for MaraTrac radio

You can see that the noise blanker in this radio, Motorola MaraTrac, is totally

turned off when the noise frequency reaches about 300 kHz. However the noise blanker

in the GE RANGR radio works in a somewhat different way. As we increase the

40

frequency of noise, the percentage of blanked noise is reduced, and it seems that the

blanker is not totally turned off no matter what the noise frequency is. This noise blanker

property is illustrated in Figure 20.

100

90

80

70 -g ~ c 60 m

CO I/) Q) 50 I/)

S Q. - 40 0

~ 0

30

20

10

0 0 50 100 150 200 250 300

Pulse Rate (kHz)

Figure 20. Noise blanker performance of RANG RI M radio

We also applied very large pulses to see if they would get past the blanker and

produce noise in the radio output. Our short, IOns pulses, produced no noise, even with

amplitude up to 7 V. But when we tried larger pulse lengths, we were able to achieve a

. low SINAD value. The data in the following table was measure~, at a fixed noise

repetition rate, 15.15 kHz (66 JlS period). We adjusted the length of the noise pulse so

41

that we could achieve a 12 dB SINAD. As we increased the pulse length of noise, we

needed to reduce the amplitude so that we could maintain a 12 dB SINAD. We repeated

the test to see the consistency of the values. The amplitude in dB}l V was measured by

peak detection on the Rohde & Schwarz ESVP receiver at 120 kHz BW with a 2 s

measurement time. We used the Motorola MaraTrac. The data are shown in Table 7.

Table 7. Noise peak amplitude vs. noise pulse width (12 dB SINAD).

Amplitude (V) 0.8 1 1.5 2 2.5 3 3.5 3.6

Amplitude(dB}lV) 48.7 50.0 54.4 56.6 59.2 60.9 60.9 61.8

Pulse Trial #1 33 16 9 3.2 2.5 2.3 2.1 1.9 length (}lSec) Trial #2 33 19 10 3.2 2.8 2.5 2.1 2.1

. 661ls pulse penod (15.15 kHz)

The noise blanker makes a blanking pulse at the leading edge of the noise pulse

with a 1 }lS delay. If the length of the noise pulse is shorter than 8 IlS (2 }lS for GE

RANGR TM) the blanker makes as many blanking pulses as noise pulses. However it

makes twice as many blanking pulses as noise pulses, if the noise has a longer pulse

length than that of the blanking pulse. This is because the blanking circuit triggers not

only at the rising edge but also at the falling edge of a noise pulse. That is not very good

because at the falling edge the blanking pulse cuts out the signal instead of the noise if

the noise pulse has a longer pulse length than that of the blanking pulse. Examples are

shown in Figures 21 and 22.

The big pulses are blanking pulses and the small pulses mark the edges of a noise

pulse. The blanking pulses were captured from the radio circuit board, but the noise pulse

42

was captured from a hybrid junction ahead of the radio antenna port. Since the hybrid

junction has limited frequency range, its output just shows the edges of the noise pulse,

which had a pulse length of 20 J.lS in figure 20 and 4 fls in Figure 21.

HP5461E8 1 2000

~.02A30 16:53:aS Tue Jun 13. 2000 501'\s/5 o.oos 10. /

.- ....... ~ ......... ~ ... "'" ·1··· .. ··· ·f···· .... t ...... ··!···· .... ·l· ...... "1·· ....... j .. . .. .. . ..

0;' ........ '.It.-I ••• ''''':- ............. :: .. _ ..... _ ... . . .. ; .••.•••• '1 ••••••.••

· . .. .. ...... 1 ::_ ._' •• I'.~'''''''' It. I;. t· •• o. .... 1 ........... 1 o. : .. .. .... .... .. .. : .................. : ............ . · .. · . . .. ; ~ · . . · . . · . · . . · . 1"'1' E· '.'1"'1'~"'1'1'1'~'1'1 01. ,. ·!.t'I'I'1

· .. ................. : ...... I ... ' ... 0., ....... I ... ~ .. I ............... : ........... I ...

~ ;! · .. · .. · .. · . -_ ..... - ... ; .... , .. 1.··· .. ·.-.::·· .. ··· __ ·;· .. ·· .. ···

-_ .... ".l. ".,,, "]' ... ···1 "" .. " i .. · .. · :·t--- --. i --.... -! -... "._j ". "." 'l""" .-

Figure 21. Noise pulses and blanking pulses of Motorola MaraTrac

l1PS461 sa Code Rev R.02.30 Wed Jun 14, 20~0 2 .OOV 1001'-.5 "eo

· . .... .......... I .......... 1 .. 1 • ,. I ,- .... ~ .................. i .............. I

· . ....••... · •..• · .• ·: ___ .····-1_·· .. · ___ ·:·······. ......... ;- ....... -:- .. ------i;---- ...... . · ..

· . ........ ·I· .. • ..... ! ......... ~ ....... . · . · . · .

.

,.","1' '1"'1'#'('1'1.2-.· ·I·I·~ ·1· ~'I'I· •• I _ "I'I'I'!'~'J'I.,.j .. 01.1.1· '1'('~'1' ·1·1·1·1·

f = : t ; I ........ • ••• III· •• !·.-·· .... ·_:_· __ ··· .. ·I .. · ........ I.I •••• ~ ••• --I ..... i .. -- ...... ___ ........... _._ ...... .

f .................. ~ .... " ... : ...... : .. : ........ + ....... 1 ••••••••• ; ••••••••• : •• '" ••••••••••••• · .. -..: :. = !. · . · .

Figure 22. Noise pulses and blanking pulses of GE RANGR ™

43

?

As part of our study of noise blankers, we also conducted the TxDOT acceptance test for

noise blanker operation. Of course both the MaraTrac and RANGR TM radio passed this

test [13].

44

CHAPTER IV

TESTS ON TxDOT TRUCKS

TxDOT vehicles

Not all the TxDOT vehicles have the installed two-way radio system, however

most of their trucks do. We tested two trucks; both were '99 Dodge Ram 1500s and could

run on either gasoline or propane. A Motorola MaraTrac radio was installed behind the

seat and the radio control box with microphone and speaker was installed under the

cigarette lighter. The radio was connected to power on with the vehicle key turned on.

There were two switches that were not installed by the manufacturer. These were the

alternate fuel (propane) switch and the light bar switch. Manufacturers do not test these

two after-market products, but they might produce noise, so we included them in our

testing. We tested the vehicles for J55114 as well as Tex-899-B compliance.

Table 8. Receiver sensitivity and ambient noise level (SAE test setup)

Receiver sensitivity BW:10kHz BW: 120kHz

Peak Avg Peak Avg

Pre-amp on, 0 dB atten -11- -10.5 -23.3 0.6 - 1.5 -12.5

Pre-amp off, 0 dB atten -3.6 - -1.9 - 15.7 8.6-9.7 - 4.7

BW: 10kHz BW: 120 kHz Ambient noise level

Peak Avg Peak Avg

Pre-amp on, 0 dB atten -6.4 - -5.8 -18 5.4-6.1 -7.2

Pre-amp off, 0 dB atten -2.5--1.4 i -14.5 9.7-10.1 -3.5

45

Table 8 gives the J55114 ambient noise level of the site where we perfonned both

tests. The ambient noise levels were read from the Rohde & Schwarz ESVP EMI

receiver, which was directly connected to the magnetic-mount antenna on top of the

vehicle roof. The receiver sensitivity is the internal noise level of the receiver, which we

measured with a 50 Q load at the input of the receiver. The scanning frequency was 47.18

MHz.

To get reliable data for the SAE J55114 test, the measurement system noise floor

should be 6 dB lower than the limit, which means we need -9 dBll V for narrow-band and

34 dBll V for broad-band noise (peak). Our receiver meets these conditions but our field

site, on the day of testing, did not meet the narrow-band condition (-6.4 ~ -5.8 vs. -9

dBllV). However, the site was much quieter than the Texas Tech University campus,

which has an ambient background noise level of 2 dBJ,lV and 42 dBllV for narrow-band

and broad-band noise, respectively.

The ambient noise level and receiver sensitivity were measured by means of the

Tex-899-B test method also and are shown in Table 9.

Table 9. Receiver sensitivity and ambient noise level (TxDOT test setup)

, Mode 6 Mode 1 ModeS

I 47.02MHz 47.18 MHz 47.34 MHz SGR I -12 dBllV R' "', ecelver sensltIvIty !

SOL 8 dBJ.lV 12 dB with load

SGA 12.3 dBJ,lV 12.3 dBllV 12.3 dBllV 12 dB with antenna

SGAL=SGA- SGL 4.3 dB 4.3 dB 4.3 dB

SGE=SGAL + SGR I - 7.7 dBIlV - 7.7 dBIlV I - 7.7 dBJ,lV

46

In this test, the Rohde & Schwarz radio communication service monitor works as

signal generator and SINAD meter at the same time. The receiver sensitivity (SGR.) is just

the amplitude of the signal generator while it is connected to the TxDOT radio and

adjusted so that the SINAD meter is reading 12 dB. Receiver sensitivity with 50 n load

(SGd is measured by the same method except for using the 3-port directional coupler

between generator and radio. See Appendix A for a diagram of the connections. Since the

directional coupler attenuates about 19.5 ± 0.5 dB from port 2 to port 1, it is reasonable

that the SGR and SGL had 20 dB difference. The signal generator is connected to port 2

and port 1 goes to the TxDOT radio. The 50 n load is connected to port 3.

For checking the ambient noise level, the antenna on top of the vehicle is

connected to port 3 while port 2 and port 1 are connected the same way as above. The

ambient noise level at the field site was 12.3 dBJ.1V. The difference (SGAL) between SGA

and SGL was 4.3 dB. The environmental noise level (SGE) is calculated by SGE=SGAL +

SGR and it should be lower than -6 dBJ.1 V. The environmental noise on the testing day

was -7.7 dBJ.1V at the frequency of 47.18 MHz

Perhaps because of their antenna differences, the ambient noise measurements on

the two trucks were slightly different. Generally the 2-5649-G truck had about 1 dB less

ambient noise, and it was true for the TxDOT and SAE tests too.

The two-way radios installed in the TxDOT trucks have 8 channels, or modes.

The frequencies of the channels are listed in Table 10.

47

Table 10. Mode number and frequency of the TxDOT radios.

Mode # Frequency (MHz)

1 47.18

2 47.06

3 47.24

4 47.26

5 47.34

6 47.02

7 47.04

8 47.08 .

Note: The whole lIst of the frequencIes used by TxDOT IS gIven In AppendIx C .

Antennas

The TxDOT trucks that we tested were equipped with Spectrum antennas with

Larsen magnetic mounts. The antennas were mounted near the center of the vehicle roof.

To determine the frequency range of the antenna on the TxDOT vehicle, we looked at the

SWR (standing wave ratio) and reflection coefficient log magnitude graphs. A network

analyzer was directly connected to the antenna on the vehicle roof for this experiment.

The scanning frequencies were from 30 MHz to 80 MHz. The SWR is defined as

1+ISII I I I

' where SI! is the reflection coefficient. The SWR graphs of the antennas show us 1 SlI

a notch-filter-like graph as we would expect. The following two graphs are the SWR

graph and SI 1 log magnitude graph of the antenna on the 2-5643-0 truck.

48

CH 1 $11 1 .,' REi=" 1 3: 2.13144

·'<V8/ ~0 2 5843 G ftt'lrEiiNA TEST , 44. 15 13'13

!'IHz

i l

I I I .l.:.~1_1;l3~L 1 Cco r' It1PR flC"P I

t t-~

l"i (, IOr MM;:I 3 I t 4; I~PRI"71

k .41· 915 ]'"' I 1 1 ~ .. ~ ~~5i:1 I

~ I

1\ k

\ r l/ \ / \

-~ \ /" \ \ I ;1 ~

I

J

f~ START

. L., • -SlOP se. £lee 090 t1H::

Figure 23. SWR of the antenna on TxDOT truck 2-5643-G

The deep valley of the SWR graph means that the antenna has the lowest

reflection coefficient at that frequency. In other words the valley frequency is the

matched frequency for the antenna. There was a slight difference in SWR graphs between

the two trucks. The 2-5643-G truck has a minimum at the 46 MHz while the other onc, 2-

5649-G, has a minimum at 47.18 MHz, which is the center of the 8 frequencies of the

radio. Hov,:ever, both truck antennas were judged satisfactory for use.

49

£Hl Sl1 log HAG 2 dE/ REF -8 dB :1:-13 aS3 dB

""<1/8/ ea 2 5643- G At'i !rENHA TEST 47. 85 Bee MHz

Car 1 -!5.~ S3 dB

4{.0 S 1"1H::: MARI<E R ~ ... IC::: .., ?::l tit:< /

""-.-.qT .~ !rh: I ! 47. ' 8 MH:: - ~ ..-::f -~b I

. -./'

\ L ~

I

/ f

V l

1 -1

S1'ARl' 30.000 000 I'1H:z STOP 8121 . 0~0 eee 11Hz

Figure 24. S))log magnitude of the antenna on TxDOT truck 2-5643-G

SAE J551/4 test results

The Rohde & Schwarz ESVP receiver was used for the SAE test. The receiver

was directly connected to the antenna on the vehicle and measured the noise value while

each of the noise sources in the vehicle were turned on. Tables 11 and 12 show the data

-from the SAE J55114 test on both trucks.

50

Table 11. SAE J55114 test results for TxDOT truck 2-5643-G

Unit: dBJlV Mode 6 Mode 1 Mode 5

47.02 MHz 47.18 MHz 47.34 MHz

Light bar on 26.1 ~30.1 27.8 - 29.8 30 - 34.8

Ignition + HV AC fan on 55.3 - 57 54.5 - 56.7 54.3 - 56.2

HVAC fan on 9.6 -16.3 10.9 - 16.0 19.5

Ignition +HV AC+Light bar on 55.6 - 59.4 54.3 - 57.2 56.1- 59

Ignition + Light bar on 53.1 ~ 58.8 53.2 - 59.1 55.1 - 59.2

Fuel pump on 6.3 5.1-6.3 4-6

Wiper on 22.7 - 29.8 25.7 - 30.5 29.8 - 34.2

Wiper with water spray on 55.9 - 60.6 49.8 - 54.1 52.8 - 56.2

Ignition + wiper on 52.4 - 53.8 52.3 ~ 55 53.8 ~ 54.6

Ignition only (propane) 52.5 - 56.3 53.0 ~ 55.3 53.2 - 56.2

Key on (propane)* 10.9-11.8 10.9 - 11.8 20 . * the key on nOIse was measured at 120 kHz bandWIdth

For the SAE test, ignition noise is the dominant noise source. Because of this, all

ignition-involved noise measurements are about the same as ignition noise itself, so the

peak measurements of ignition noise with some other noise sources are not very

important in this test. For that reason, some of the noise tests on the 2-5649-G truck are

omitted.

51

Table 12. SAE J551/4 test results for TxDOT truck 2-5649-G

Unit: dBttV Mode 6

47.02 MHz

Light bar on 43.3 - 47

Ignition + HV AC fan on 48 ~ 54.2

HVACfanon 10.5 - 11.7

Ignition +HV AC+ Light bar 51.3 - 53.9

on

Ignition + Light bar on 51.3 - 53.9

Fuel pump on 11 - 13.5

Wiper on 31.3 - 35.2

Wiper with water spray on 52 - 54.9

Ignition + wiper on 53.4 - 54.3

Ignition only (propane) 49.7 - 54.5

Key on (propane)*** -2.6

gasol* : gasoline is used for the engine idle

prop* : propane is used for the engine idle

* * : not tested

Mode 1 47.18 MHz

39~43

**

12.4 - 8.3

** >'

**

8.3 - 9.6

38-39

54-58

**

53.2 - 54.6(prop*) 54.5 - 55.0(gasol*)

-1.4

* * * : key on noise was measured at 10kHz bandwidth

Mode 5 47.34 MHz

44-46

52.7 - 54.8

15.7-17

52.2 - 53.4

50.4 - 52.1

10.3 - 12.4

28.9 - 32.4

49.1 - 54.3

53.2 - 55.2

52 - 53.9

9.7

After spark ignition noise and wiper with water spray, the light bar is the highest

noise contributor in the SAE test. The two trucks have light bars in different locations.

One of them has the light bar installed on the roof about 2 inches away from the antenna,

while the other one has the light bar on the top of the headache rack. For the 2-5649-G

truck, which has the light bar near the antenna, the measured value of the noise from the

52

light bar is higher than our new SAE J551/4 test limit, 40 dB~V, for broad-band noise.

The light bars on both trucks have no visible filters installed, but the peak value of noise

from the light bar was reduced about 6 dB when two ferrite chokes were placed on the

light bar wire. However, we found that the noise from the fuel pump and HV AC fan is

very quiet and far from our 40 dB~ V limit, so they evidently have installed noise­

reducing filters.

We had a chance to test in our laboratory a different light bar from TxDOT. It has

two more motors in it and has filters installed on all of the motors (see Chapter Ill). The

filter is composed of three capacitors soldered onto the back of the motor. We tested the

light bar with the filters and without the filters as well. Although this light bar produces

lower noise, it is enough to see the effect of the filter. With the filter installed the noise of

the light bar was reduced by 20 dB and it had a peak amplitude at 33 MHz.

When we performed the vehicle tests with key on, a new type of noise was

observed. It is probably generated from micro-controllers (so-called "modules"). The

peak value of this noise stayed around -2 dB~V until the frequency reached 47.34 MHz,

which is the highest TxDOT frequency. After 47.34 MHz the peak values went up by 17

dB until the frequency reached 47.53 MHz and then went back down to -2 dB~V. The

graph in Figure 25 shows frequency scans obtained by the ESVP receiver. The bandwidth

of this measurement was 10kHz and the frequency step size was 5 kHz. The key on with

propane and key on with gasoline produce almost the same noise. The key-on noise in

this chapter is key on with propane. (The key-orinoise values in table 9 were measured

53

with 120 kHz bandwidth and the values in table 10 were measured with 10kHz

bandwidth.) The occasional large peak occurred when a car passed by the test site.

> ::l co ~ CD "0

~ 0. E et:

30

25

20

15

10

5

,

; t 1E\S

~~ .. 0 0./\. p"'Q

kO·00.e-e-i '\0'e~ Q"o<'.0-e'Oo-o.6 \,.0' -10

-15~--~----------~----------~------------~----------~----~ 47.3 47.35 47.4

Frequency (MHz) 47.45 47.5

( _._ ............. -... - : ambient noise only, --- : ambient + module noise)

Figure 25. Frequency scan of module noise and ambient noise

This noise from the modules spreads about 150 kHz wide, so it looks more like

broad·band noise than narrow·band noise. We compared the peak and average value for

this noise at 47.37 MHz using 10 kHz bandwidth. The values are shown in table 13.

There is about 16 dB difference between peak and average. From the guideline of the

54

SAE test, if a 10kHz bandwidth measurement for peak and average values of the noise

shows more than a 6 dB difference, the noise should be treated as broad-band noise. Thus

the noise from the modules is broad-band.

Table 13. Peak and average value comparison of key-on noise (2-5643-G)

Unit: dBJ.l V Peak value Average value

Key on (gasoline) 15.2 -0.4

Key on (propane) 15.6 I -1.3

Notes: frequency::=; 47.37 MHz

When we hooked up the AM output of the ESVP receiver to a Fluke portable

oscilloscope, we observed the waveforms of the module noise. The oscillograms in figure

26 show some examples. The frequency was 47.34 MHz.

1i5.5VDC1.l!)':1 . (;l2vOFFle: 1 1;00;;-. :' ~2J".Jpf:-:rH;r,.:r-~~~.:.A~:-.4Qr~· ... :.- . ~ ": ... ~ /flflNL~"l.-. .. -. .. .. .. .. .. ... ..

~ , "'i, ., 'l , ... f" .. ~ .. , .~ .... ~ .... ~ .. "~ .. "j .. .... '. M','" _. _ _...... .. .. "".. .. • _

.. . . j . ... - .... ..... ' ......... ............... - "",.-. "' ............... ..

--WaveForm A: Vpeak:(:,peak Vrms ·1&6· V 11.0 V

(a)

55

I

5VOC 18:t [;3 2VOFF18:1 11 00 iili ' V TRIG :A"'L -2DIV· MANUAL

" .............. '. " .. wo ." _ .......... _. " •• ""' .. *'... .. '" .. " ._ .. "".~ -... -. iJ; •

. I . ..

". ." '" " • .. .. .. .. .. ,. ... ,., .. ,. .. 10 .. ., '" .. .. • .. .. .. .. .. _. ..

.-WaveForm A:

Vpeak/pt;aak Vrms

16.8 V 11.0 V

(b)

m 'r- ;:;.08'.1 7- 180.LJ:S [l;!..... 18. 8\1 ~5 .88ms ......... " " .... " ........ ~ ...... " ........ - "" '" ......... - .. '"' ... ,. ....... " ~ "." ...... , . , . ,

-.3:1. - • I . . - - -:?'tA:?'t -litJlll11!._ . : :MANUAL .. - - • - .. .. ,.. "" .. ... .. .. ~ .. • .. .. .. .. _. .. " .. ~ .. , " .. .. • ,,-. .. I .. ~ " .. .. ... .. "." .. .. .. ..

1(). : ..

.. . .. ... .. .. - .. -.. '"' ..... "." .. ,.

J.rJavef"orm A:

Vpeak/pe:3k Vrms

200 mv 200 mv

(c)

Figure 26_ Noise from module (key-on noise)

56

From figure 26 (a) we found that the waveform has 2 kHz pulse rate and 90 kHz

bunch rate. Switching the noise blanker in the MaraTrac radio on and off had no effect

on these pUlses. The ESVP receiver has an FM output also, and it would be interesting to

see what FM content these pulses might have.

TxDOT Tex-899-B test results

The Rohde & Schwarz radio communication service monitor was used with the

installed radios for the Tex-899-B test. The values in the next two tables indicate the

amplitude of the signal needed to obtain a 12 dB SINAD reading with the corresponding

noise source. The 3-port directional coupler was used to combine the FM signal and noise

from the antenna as described previously.

Table 14. TxDOT Tex-899-B test results for TxDOT truck 2-5643-G

, Unit: dBJlV

Mode 6 Mode 1 ModeS 47.02MHz 47.18 MHz 47.34 MHz

Light bar 16 15.6 19.9 Wiper 16.2 15 18

f-.; 15 14.8 18.6 ,HVACfan

I Fuel pump 13.9 13.6 15.1

: Key on (propane) 15 14.7 18.4

Key on (gasoline) 14.7 14.3 18.3 ! ALL VEHICLE SYSTEMS ON (GASOLINE)

SGA 17.4 dB~V 18.2 dB~V 19.6 dB~V 12 dB with antenna

SGAL =SGA - SGL 9.4 dB 10.2 dB 11.6 dB

SGE=SGAL + SGR - 2.6 dB~V - 1.8 dB~V - 0.4 dBJlV ALL VEHICLE SYSTEMS ON (PROPANE)

SGA 17.4 dB~V 17.6 dB~V 19.6 dBJlV 12 dB with antenna

SGAL=SGA - SGL 9.4 dB 9.6 dB 11.6 dB

SGE=SGAL+ SGR - 2.6 dBJlV - 2.4 dB~V I - 0.4 dBJlV ~ - ~-

!

57

From the "all vehicle systems on" value, we can see that the 2-5649-G truck

failed the Tex-899-B test by 0.1 dB when running on gasoline. In individual noise tests,

key-on noise is the highest contributor at 47.34 MHz. The 0.5 dB difference between

trucks for "all vehicle systems on" noise makes the 2-5643-G truck pass the Tex-899-B

test. However. it also has strong key-on noise. From all the data. we can see there is no

big difference in noise when the vehicles run on gasoline or propane.

Table 15. TxDOT Tex-899-B test results for TxDOT truck 2-5649-G

Unit: dBJlV Mode 6 Mode 1 ModeS

47.02MHz 47.18 MHz 47.34MHz

Light bar 12.2 11.9 13.7

Wiper 13.0 15.3 16.7

HVACfan 12.5 12.5 15.9

Fuel pump 13.2 12.9 12.5

HV AC fan + fuel pump 13.8 13.2 17.9

Turn signal 12.2 11.9 12.3

Key on (propane) 13.1 12.7 17.7

Key on (gasoline) 13.2 12.9 15.8

ALL VEHICLE SYSTEMS ON (GASOLINE)

SGA 16 dBJlV 16 dBJlV 20.1 dBJlV 11 dB with antenna

.~.-- .~

SGAL=SGA- SGL 8 dB 8dB 12.1 dB

SGE=SGAL+ SGR -4dBJlV - 4 dBJlV 0.1 dBJlV

ALL VEHICLE SYSTEMS ON (PROPANE)

SGA 16.2 dBJlV 16 dBJlV 19.5 dBJlV

12 dB with antenna

SGAL=SGA- SGL 8.2 dB 8 dB 11.5 dB

SGE=SGAL + SGR -3.8 dBJlV - 4 dBJlV - 0.5 dBJlV L-___ --

58

Truck test summary

In the J55114 test the spark ignition noise was the strongest, as expected, with one

small exception. When running the windshield wiper and activating the washer, peak

noise levels comparable to ignition noise were observed. The culprit was the washer

motor. However the very intermittent nature of this source makes it questionable as to

whether it should be of concern.

The next strongest noise sources were the light bar on the 5649 truck, followed by

the light bar on the 5643 truck and the windshield wipers and then the HVAC fans and

fuel pumps

In the Tex-899-B test the various vehicle noise sources were all rather weak

except for the key-on noise at 47.34 MHz. At this frequency, with all vehicle systems on,

the key-on noise together with the other noise sources was sufficient to put the vehicles

essentially at the TxDOT limit.

An objective of the truck testing was to validate the new limits for DC-motor

noise: 50 dBJlV for one motor, and 40 dBJlV for two motors of comparable noise output.

These limits were derived from our bench-top simulation where the two motors were an

HV AC fan and a fuel pwnp.

Unfortunately we were unable to accomplish the validation, as far as HV AC fans

and fuel pumps are concerned, because the noise from the fans and fuel pumps in the

vehicles was low, much lower than expected. However the noise from two other DC­

motor sources provided important new information. The light bar, with its two motors,

59

generated noise above the 40 dBJ.1 V limit and the windshield washer, with one motor,

generated noise above the 50 dBJ.1 V limit. Yet neither light bar nor washer motors

exceeded the Tex-899-B limit. That is, the noise produced by the tiny motors in the light

bar and washer has less effect on the TxDOT radio than expected (due possibly to the

effect of the noise blanker in the TxDOT radio), and thus these motors must have a

higher J55114 limit placed on them than the limit for fan and fuel pump motors.

60

Limit for narrow-band noise

CHAPTER V

CONCLUSIONS

Narrow-band noise emission is due to microcontrollers and their associated

circuitry. The current narrow-band noise limit for the SAE J551/4 test is 0 dBJ..lV. This

limit is too high to match the Tex-899-B test. The Tex-899-B test restricts its maximum

input FM signal to 1 J..lV (= 0 dBf.lV). Since the noise level should be at least a few dB

lower than the signal amplitude for good reception, with no doubt, the current limit for

the narrow-band noise should be decreased.

The suggested new limit for narrow-band noise peak amplitude is -3 dBJ..lV. This

value is obtained from the data plotted in Figure 27. The experiments were performed

three times to test the repeatability of the noise. Except for one curve, all curves are just

slightly higher than -3 dBf.lV until the fan noise peak amplitude reaches 40 dBJ..lV. We

used a Motorola MaraTrac radio, since this radio is the newest in the TxDOT vehicle

fleet.

Limit for broad-band noise

Broad-band noise emission is mostly caused by DC motors and spark ignition.

DC motor noise is emitted from the fuel pump, HV AC fan and radiator fan. The noise

emission from DC motors has inherent randomness, which causes a 2 dB standard

deviation even with 2 second measure time.

61

6~-------'--------'-------~--------~------~------~

5 ;;-tff -0 -CD4 -0 ::J :t: 0. E

~3 tU CD a.. CD (I)

~2 c tU

LL ()

~1 :r:

o 0 0 0 0 0 0 0 0 ODD 0 0 0 0 0 0

x x x x x x x x x x x x x x x x x x x

0

0

0

0

0

V

-3 o~------~------~------~------~------~------~ ~ ~ ~ ~ 4

CW Noise Peak Amplitude (dB).!V) -2

V: TxDOT Tex-899-B test result for combined noise

0: Suggested limit ofSAEJ55114 test for narrow-ban.d noise and DC motor noise

x: Current limit ofSAE J551/4 test

Figure 27. Modified SAE J55114 limits and TxDOT Tex-899-B limit for combination of CW and HV AC fan noise using Motorola MaraTrac Radio

Using a Motorola MaraTrac radio, we found the RV AC fan noise peak value for

12 dB SINAD is between 50 and 55 dB).! V. This value decreased a bit when we added

other DC-motor noise such as fuel pump, radiator fan and wiper noise. However, the

current limit of the SAE 155114 test for broad-band noise is 28 dB).!V, which is too low.

62

The suggested new limit for emissions from multiple DC motors is 40 dB/-l V and this is

plotted in Figure 27. This value is reasonable because the maximum DC-motor noise

measured from nine TxDOT vehicles was 37 dBIlV and they all passed the Tex-899-B

test. [7]

During the SAE vehicle tests we found that the spark ignition system generates

more noise than the noise from DC motors. However spark ignition noise had no effect

on the SINAD test. This is because the noise blanker in the TxDOT radio is very

effective for spark ignition noise while considerably less effective for DC-motor noise. In

the bench-top test for the spark ignition noise itself we could not achieve 12 dB SINAD.

Even at the maximum output of our spark ignition simulator, the SINAD value was 28

dB. The maximum output of this pulse generator was 11 volts which is 88 dB/-l V at 47

MHz. In the vehicle test, we found the maximum spark ignition noise peak is at 56

dB/-lV. That means we applied 30 dB above the highest peak value of the practical spark

ignition noise, but the SINAD still stayed at 28 dB. Hence, the limit for spark ignition

noise is a lot higher than the limit for DC-motor noise, and each broad-band noise

emission needs to be measured separately with a different limit.

The broad-band noise limit for the light bar needs to be somewhat higher than

that for the HV AC fan. For one truck we tested, the light bar produced 43 dB/-lV peak

noise but it passed the Tex-899-B test, so the broad-band noise limit for the light bar

should be higher than the 40 dB/-l V limit for the HV AC fan.

63

Modified SAE J55114 test

As discussed in the two previous sections, the modified new limits for narrow­

band noise and DC-motor noise are -3 dBf.1V and 40 dBf.1V, respectively. Table 16 shows

the suggested SAE J55114 test limits and corresponding bandwidth of measuring

equipment for each noise source. The limits of the measurement system's noise floor

need to be at least 6 dB lower than the noise limits for the test. Thus the narrow-band and

broad-band noise floor limits for the system should be -9 dBf.1V and 34 dBf.1V,

respectively. Table 16 also gives the test procedure (or steps) for the modified SAE

J55114 test.

Although methods and units of output data for both tests are different, the

modified SAE J551/4 test shows a better correlation with the Tex-899-B test and can be

substituted for it. Since the SAE J55114 test measures the noise directly from the antenna

by using an EMI receiver or spectrum analyzer, it's easy to set up and less time

consuming. Also, with the use of computer control, this test allows for automatic

measurement of data at many different frequencies. If the measurement is perfonned by a

spectrum analyzer, the data can even be visualized as a frequency-domain plot. This is a

very attractive aspect of the SAE test. Therefore the modified SAE J55114 test provides

not just an alternative to the Tex-899-B test but also provides better test efficiency.

64

Table 16. Modified SAE J55114 test procedure

Vehicle status Measuring Limits of

terminal Noise voltage at instrument

receiver antenna tenninal Noise type (Engine warm Bandwidth

[dBJiV] before testing) [kHz]

Peak Detection Measurement system

I.Alloff 10 -9 narrow-band noise floor (ambient noise)

Measurement system 2.All off 120 34 broad-band noise floor

(ambient noise)

3.Engine off, key on 10 -3 Narrow-band noise

from microcontroller

4.Engine off, key on; fuel pump on,

120 40 Broad-band noise

wiper on, radiator from DC motor fan on

5.Engine on 120 >88 (broad-band noise)

Future work

A conclusion from figure 16 is that the noise blanker in the Motorola MaraTrac

radio is more effective than the blanker in the GE RANGR TM at reducing fan noise. This

may be due to the fact that the MaraTrac has a longer blanking pulse than the

RANGR™, as seen in Figures 20 and 21. Perhaps even better noise-blanker performance

could be obtained by modifying the radio to provide an even longer blanking pulse.

The results of our tests of TxDOT vehicles (chapter IV) show that we must apply

different limits to the peak values of the emissions from different types of DC motors.

This is a nuisance. One would like to have a single limit for all DC motors. A possible

65

alternative is to use the average value of the emissions rather than the peak value. lbis

might result in a single limit and is an area worth investigating.

The key-on noise we observed in the TxDOT vehicles (Figures 25 and 26) is of a

type we had not previously seen: amplitude modulated and with a bandwidth of about

150 kHz. It is evidently produced by electronic modules in the vehicles. Such noise is

likely to become more common in future vehicles. It requires laboratory study and

assignment of a limit.

66

REFERENCES

L American Radio Relay League (ARRL) Inc., Automotive Interference Solution, 1999, Newington, CT - www.arrl.orgltis/info/rfiauto.html

2. Century Performance Center., Spark Plug Tech, 1997, Reno, NV www.centuryperformance.comlsparkl.htm#Spark%20Plug%20Types%20and%2 ODesigns:

3. FCC regulations title 47 telecommunication, chapter I, part 15 - radio frequency devices -- Table of Contents, Subpart C--Intentional Radiators page 634--705.

4. SAE, Surface Vehicle Electromagnetic Compatibility (EMC) Standards Manual, 1997, Society of Automotive Engineers Inc, Warrendale, P A.

5. CISPR 25, "Limits and Methods of measurement of radio disturbance characteristics for the protection of receivers used on board vehicles," 1995-11, International Electroteclmical Commission, Geneva, Switzerland.

6. Ye lin, Laboratory Simulation of Motor Vehicles Radio Interference, 1998, Master thesis in Electrical Engineering Department at Texas Tech University

7. Qianlin Zhou, Testing Motor Vehicle for Radio Interference,1998, Master thesis in Electrical Engineering Department at Texas Tech University

8. Edward N. Skomal, Man-made Radio Noise, 1978, Van Nostrand Reinhold Company, New York.

9. CISPR 16-1, "Specification for radio disturbance and immunity measuring apparatus and methods, Part 1: Radio disturbance and immunity measuring apparatus," 1993, International Electrotechnical Commission, Geneva, Switzerland.

10. TIA/ErA Standard TIAlEIA-603, "Land Mobile FM or PM communications Equipment Measurement and Performance Standards," Telecommunications Industry Association, Washington, DC, February 1993.

11. Boaz Porat, A Course in Digital Signal Processing, 1997, John Wiley & Sons, Inc, New York.

12. Albert A. Smith, Jr, Radio Frequency Principles and Applications: The generation, propagation, and reception of signals and noise, 1996, IEEE PressiChapman & Hall Publishers Series on Microwave Technology and RF.

67

13. Richard Hemdon, TxDOT, Austin TX, April, 1999, private communication

68

APPENDIX A

Tx:DOT Tex-899-B TEST

RADIO FREQUENCY INTEFERENCE (RFI) TESTING

This test method assures the compatibility of Texas Department of Transportation (TxDOT) fleet vehicles and VHF FM radio equipment operating in the frequency ranges of 30 to 50 MHz and 150 to 174 MHz, but not inclusive. It is intended to identify 90% or more ingress and egress problems.

DefInitions

Ingress - any action, reaction, indication, failure to perform or comply, by vehicle equipment and/or accessory items, caused by the activation of the VHF FM radio transmitter in any mode of operation.

Egress - any mode of operation, action, reaction or indication or by the vehicle equipment and/or accessory equipment which degrades the VHF-FM radio receiver effective sensitivity performance by more than six dB.

Eguipment

• 100 watt VHF FM communications transmitter and receiver capable of operating on all Tx:DOT frequencies.

• 12 V regulated DC power supply • RF signal generator with a calibrated attenuator • Signal-to-noise audio distortion (SINAD) meter • Receiver audio termination load • RF directional coupler rated at 40 dB directional, minimum • RF termination load • Magnetic mount antenna for the testing frequencies • RF isolation choke, a (6 ft. by 6 ft.) sheet of hardware cloth, laid flat on

the test area floor with the coaxial cable making one complete loop approximately four feet in diameter under it

• RF wattmeter

Facilities

• Free of high ambient RF noise (receiver test) • Equipped with lift capable of raising vehicle tires six inches above floor

(transmission test)

69

Safety notes

Safety be must never be compromised during tests. Hazards due to vehicle parts moving and radio frequency/electrical bums exist. Strict compliance with accepted work practices must be observed at all times. Sudden actions may result when the radio transmitter is activated. Stay clear of vehicle and antenna. One person should operate the vehicle, and another the radio.

Egress compatibility

• Receiver qualification

Step Action

1 Assemble a test set-up as shown figure 1

2 Generate a standard test signal and establish 12 dB SINAD

3 Record receiver basic sensitivity. . ~ ..

4 Increase signal 6 dB above step 3.

5 Increase peak deviation until SINAD is degraded to 12 dB SINAD

6 Record modulation acceptance (Bandwidth)

Compliance of the test setup qualifies the receiver for acceptance testing if:

the receiver basic sensitivity is less than 0.4 J.lV(-114 dBm) for 12dB SINAD The receiver bandwidth shall be a minimum of ± 6.5 kHz and a maximum of± 8.0kHz.

FM Modulated Test radio Audio Signal Generator RF cable RXaudio termination Load

I I DC Power SINADMeter

supply

Figure 1

70

• Site Qualification

Step Action

1 Assemble a test set-up as shown in figure 2.

2 Move test vehicle into radio frequency interference shield room or onto site.

3 Temporarily install the magnetic mount antenna on the center of the vehicle loop.

4 Disconnect the battery cable.

S Terminate the RF line into the RF load terminal.

6 Generate a standard test signal of on-channel center frequency FM modulated with a 1 kHz sine wave tone at ±3.3 kHz deviation.

7 Increase the signal generator RF output level until a 12 dB SINAD indication is achieved.

8 Record sensitivity into RP road termination in dBm.

9 Remove the RF load termination and terminate the RF line into the temporary antenna.

10 Increase signal generator RF output level until a 12 dB SINAD indication is achieved.

11 Record sensitivity into antenna in dBm.

12 C:ompute the effective sensitivity and determine if the site is ualified.

:tepeat site qualification at all test radio channels/frequencies to be used

RF cable .. RP Isolation RF cable Test RX audio Audio tennination

tion RF

Tennina Load

~ Coupler

I FM Modulated

Signal Generator

Figure - 2

71

Radio output Load

I I DC power STNAD

supply Meter

• Effective Sensitivity Calculation

Step Action

1 Subtract the sensitivity into antenna from sensitivity into RP load termination.

2 Record this difference.

3 Subtract this difference from the basic receiver sensitivity.

4 Record the effective receiver sensitivity in dBm.

5 Convert the effective receiver sensitivity to microvolts.

• Site Qualification Standards

The site is qualified if the effective receiver sensitivity is less than 0.5 f-L V (-113dBm)

72

Egress compatibility

• Egress compliance test for test for test vehicle

Step

1

2

3

4

5

6

7

8

9

10

Action

Reconnect vehicle battery.

Increase the signal generator RF output level until a 12 dB SINAD indication is achieved.

Record the signal generator RF output level.

Activate one vehicle system or accessory.

Increase the signal generator output level until a 12 dB SINAD indication is achieved.

! Record the signal generator RF output level.

Repeat Steps 4 through 6 until all vehicle systems and accessories are activated.

Compute total degradation. See NOTE.

Repeat compliance test for all test radio channels/frequencies to be used.

Turn off engine.

NOTE: The electrical system should be designed so the effective sensitivity of the VHF FM receiver requires not more than 1 J.l V (-107 dBm) to produce 12 dB or greater SINAD. The effective sensitivity should not exceed 1 J.l V for all modes of operation, which should include engine off, engine on, (from idle to full throttle), and all vehicle systems or any combination thereof

• Test vehicle qualification

The test vehicle passes the egress compliance test when the total degradation does not exceed 6 dB

73

Ingress compatibility

• Antenna qualification

Step Action

1 Assemble a test set-up as shown in Figure 3.

2 Verify engine is OFF.

~aise test vehicle (6 in.) offfloor.

4 Verify that magnetic mount antenna IS mounted III center of vehicle roof.

5 Key microphone on test radio.

6 Record nominal forward RF power to the antenna.

7 Record rectified RF power from the antenna.

Adjust length of antenna, if needed, and repeat steps5 through 7 8 until nominal forward power is 100 watts ± 10 watt and reflected

power is less than 10 % of the forward power.

Vehicle Roof

6.096 m 3.048 m Temporary (20 ft) RF (10 ft) RF Test Magnetic Isolation Watt I--- Radio Antenna RG-58 Choke RG-58 Meter

Coaxial Coaxial Cable Cable

I "-

DC Power

Not Less Than 10ft Horizontal Supply ...

Distance ..

Figure 3.

74

Vehicle Qualification for Acceptance

Step Action

1 Start vehicle.

2 Put vehicle in gear and rotate tires at a moderate speed.

3 Activate one vehicle system or accessory. Be certain to check the braking operation.

4 Activate the radio transmitter for approximately five seconds.

Record results as one of the following:

5 1. No adverse reaction 2. Reaction resulting in safety hazard 3. Reaction resulting in a nuisance operation.

6 Repeat steps 3 through 5 until all vehicle systems and accessories are activated.

7 Repeat vehicle qualification for all test radio channels/frequencies to be used.

8 Stop wheels of vehicle and turn off engine.

Vehicle Qualification Results

Safety Hazard - No vehicle system and/or accessory shall operate and/or fail to operate as a result of the activation of the VHF FM radio transmitter in a manner which constitutes a safety hazard.

Nuisance operation - correct nuisance operations of any vehicle system and/or accessory.

Failure to meet the criteria of this test method will result in rejection of the vehicle.

75

APPENDIXB

SAE J55114 TEST

Test limit and methods of measurement of radio disturbance characteristics of vehicles and devices, broadband and narrowband, 150 kHz to 1000 MHz

Forward This SAE standard is based on CISPR 25 which has been developed by CISPR Subcommittee D and has been approved to be published. The SAE Electromagnetic Radiation Committee has been an active participant in Subcommittee D and in the development of CISPR 25.

This document provide test limits and procedures for the" protection of vehicle receiver from radio frequency (RF) emission caused by on-board vehicle components"

NOTE - Appendix II provides helpful methodology for resolution of interference problems.

Table of Contents

1. Scope .......... , .............................................. '" ....................................... 2

2. References ............................................................................................. 3 2.1 Applicable documents ................................................................................ .3 2.1.1 SAE publication ....................................................................................... .3 2.1.2 CISPR publication .................................................................................... .3

3. Definition ............................................................................................... 3

4. Requirements Common to vehicle and Component/Module Emission Measurement.. .... 3 4.1 General Test Requirements and test plan.3 ......................................................... 3 4.1.1 Test Plan Notes ....................................................................................... 3 4.1.2 Determination of Confonnance with Limit ......................................................... 3 4.1.3 Category of Disturbance Sources(as applied in the test plan) ................................... 3 4.1.4 Example of Broadband Disturbance Sources ...................................................... 5 4.1.5 Narrowband Disturbance Sources ................................................................... 5 4.1.6 Operating Conditions ................................................................................. 5 4.1.7 Test Report ............................................................................................. 5 4.2 Measuring Equipment Requirement.. .............................................................. 5 4.3 Shield Enclosure ....................................................................................... 5 4.4 Absorber Lined Shield Enclosure (ALSE) ........................................................ 5 4.4.1 Reflection Characteristic ............................................................................. 6 4.4.2 Objects in ALSE ....................................................................................... 6

SAE Technical Stindards Board Rules provide that this report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement ansing therefrom, is the sole responsibility of the user.

SAE reviews each technical report at least every five years at which time it may be reaffinned, revised or cancelled. SAE invites your written comments and suggestions.

76

4.5 Receiver. ................................................................................................ 6 4.5.1 Minimum Scan Time ................................................................................. 6 4.5.2 Measuring Instrument Bandwidth ................................................................... 6

5. Antenna and Impedance Matching Requirements - Vehicle Test ........................... 7 5.1. Type of Antenna ....................................................................................... 7 5.2. Measurement System Requirements .............................................................. 7 5.2.1 Broadcast Bands ...................................................................................... 7 5.2.2 Communication Bands (30 to 1000 MHz) ......................................................... 8

6. Method of Measurement .............................................................................. 9

7. Limits for Vehicle Radiated Disturbance ........................................................... 9

Appendix I Appendix II

Antenna Matching Unit Vehicle Test.. .............................................. 12 Notes on the Suppression ofInterference ................................................ 14

Figure 1 Method of Detennination of Confonnance of Radiated/Conducted Disturbance ........... .4 Figure 2 Example Gain Curve ................................................................................. 8 Figure 3 Vehicle Radiated Emissions-example for test layout (End view with monopole antenna) ... 10

Table I Table 2 Table 3 Table 4 Table 5

Examples of Broadband Disturbance Sources by Duration ............................ 5 Minimum Scan Time ........................................................................ 6 Measuring Instrument Bandwidth (6 dB) ......... '" ..................................... 7 Antenna Types .............................................................................. 7 Lim its of Disturbance - Complete Vehicle .............................................. 11

1. scope - this SAE Standard contains test limits! and procedures for the measurement of radio disturbances in the frequency range of 150 kHz to 1000MHz. The document applies to any electronic/electrical component intended for use in vehicles. Refer to International Telecommunication Union (ITU) Publications for details of frequency allocations. The tests are intended to provide protection for receivers installed in a vehicle from disturbances produced by components/modules in the same vehicle2

.

The receiver types to be protected are: broadcast radio and TV), land-mobile radio, radio telephone, amateur and citizens' radio.

The limits in this document are recommended and subject to modification as agreed between the vehicle manufacturer and the component supplier. This document shall also be applied by manufacturers and suppliers of components and equipment, which are to be added and connected to the vehicle harness or to an on-board power connector after delivery of the vehicle.

This document does not include protection of electronic control systems from RF emissions, or from transient or pulse type voltage fluctuations. These subjects are covered in other sections ofSAE J551 and in SAE .T11l3.

I only a vehicle can be used to determine the component compatibility to a vehicle limit. 2 adjacent vehicle can be expected to be protected in most situations. 3 adequate TV protection will result from compliance with the levels at the mobile service frequencies

77

The Word Administrative Radiocommunications conference (WARC) lower frequency limit in region I was reduced to 148.5 kHz in 1979. For vehicular purposes, test at 150kHz are considered adequate. For the purpose of this document, test frequency ranges have been genemlized to cover radio services in various parts of the world. Protection of radio reception at adjacent frequencies can be expected in most cases.

2. References

2.1 Applicable Documents - the following publications contain prOVlSlons which, through reference in this text, constitute provisions of this document. At the time of publication, the editions indicated were valid. All documents are subject to revision, and parties to agreements based on this document are encouraged to investigate the possibility of applying the most recent editions of the documents indicated. Members of IEC and ISO maintain registers of currently valid International standards.

2.2.1SAE Publication - Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.

SAE J551/1 MAR94 - Performance Level and Method of Measurement of Electromagnetic Compatibility of Vehicle and Devices (60 Hz to 18 GHz)

2.1.2 CISPR Publication Available from ???

CISPRI6-1: 1993-08-Specification for Radio Disturbance and Immunity Measuring Apparatus and Methods. Part I: Radio disturbance and immunity measuring apparatus

3. Definitions - See SAE J55111.

4. Requirements common to vehicle and component/module emissions measurement

4.1 General Test Requirements and Test Plan

4.1.1 Test Plan Notes A test plan should be established for each item to be tested. The test plan should specified the frequency range to be tested, the emission limits, the disturbance classification [Broad Band (long or short duration) Narrow Band], antenna types and locations, test report requirements, supply voltage, and other relevant parameters.

4.1.2 Determination of Conformation with Limits - If the type of disturbance is unknown, test should be made to determine whether measured emissions are narrow band and/or broad band to apply limits properly as specified in the test plan. Figure 1 outlines the procedure to be followed in determining conformance with limits.

4.1.3 Categories of Disturbance Sources (as applied in the test plan) - Electromagnetic disturbance sources can be divided into three types:4

a. Continuousllong duration broadband and automatically actuated short duration devices b. Manually actuated short duration broadband c. Narrowband

4 For example see 4.1.4 and 4.1.5 and Table 1.

78

MEASURE EUT USING TIIE PEAK. DETECTOR

NO

IS THE DIFFERENCE BETWEEN PEAK AND A VERAGE GREATER

THAN6dB?

START

MEASURE EUT USING TIIE PEAK. DETECTOR

ARE THE DATA BELOW THE

NARROWBAND LIMIT?

DETERMINED TO BE NARROWBAND

DETERMINE TO BE BROADBAND (REMEASURE WITH QUASIPEAK

DETECTOR. IF REQUIRED BY TEST PLAN

NO ARE THE

BROADBAND DATA BELOW THE BROAD

BAND LIMIT ?

FIGURE 1 - METHOD OF DETERMINATION OF CONFORMANCE OF RADIATED/CONDUCTED DISTURBANCE

79

YES

4.1.4 Example of Broadband Disturbance sources

Note - The Examples in table 1 are intended as a guide to assist in detennining which test limits to use in the test plan.

Table 1- Example of Broadband Disturbance Sources by Duration.

Continuous Long Duration l Short Duration l

Ignition system Active ride control Fuel injection Instrument regulator Alternator

Wiper motor Heater blower motor Rear wiper motor Air conditioning compressor Engine cooling

defined in the test plan

Power antenna Washer pump motor Door mirror motor Central door lock Power seat

4.1.5 Narrowband Disturbance Sources - Disturbances from sources employing micro processors, digital logic, oscillators or clock generators, etc., cause narrowband emissions.

4.1.6 Operating Conditions All continuous and long duration system shall be operated at their maximum RF noise creating conditions. All intennittently operating systems (i.e., thennostatically controlled) that can operate continuously, safely, shall be caused to operate continuously.

When perfonning the narrowband test , Broadband sources (i.e., ignition system, in particular) may create noise of higher amplitude. In this situation, it will be necessary to test for narrowband noise with ignition switch ON, but the engine not running

4.1.7. Test Report - The report shall contain the infonnation agreed upon by the customer and the supplier

4.2. Shielded Enclosure - The ambient electromagnetic noise levels shall be at least 6 dB below the test limits specified in the test plan for each test to be perfonned. The shielding effectiveness of the shielded enclosure shall be sufficient to assure that the required ambient electromagnetic noise level requirement is met.

The shielded enclosure shall be of sufficient size to ensure that neither the vehiclelEUT nor the test antenna shall be closer than (a) 2 m from the walls or ceiling, and (b)lm to the nearest surface of the absorber material used.

4.4. Absorber-Lined Shielded Enclosure (ALSE) - For radiated emission measurements, however, the reflected energy can cause errors of such as 20 dB. Therefore, it is necessary to apply RF absorber material to the walls and ceiling of a shielded enclosure that is to be used for radiated emission measurements. No absorber material is required for the floor. The following ALSE requirement shall also be met for perfonning radiated RF emission measurements:

80

4.4.1 Reflection Characteristics - The reflection characteristic of the ALSE shall be such that the maximum error caused by reflected energy from the wall and ceiling is less than 6 dB in the frequency range of 70 to 1000 MHz.

4.4.2 Objects in ALSE - In particular, for radiated emission measurements the ALSE shall be cleared of all items not pertinent to the tests. This is required in order to reduce any effect they may have on the measurement. Included are unnecessary equipment, cable racks, storage cabinets, desks, etc. Personnel not actively involved in the test shall be excluded from the ALSE.

4.5 Receiver - Scanning receivers which meet the requirements of CISPER 16 are satisfactory for measurements. Manual or automatic frequency scanning may be used. Spectrum analyzer and scanning receivers are particularly useful for interference measurements. Special consideration shall be given overload linearity, selectivity, and the normal response for pulses. The peak detection made by spectrum analyzer and scanning receiver provides a display indication which is never less than the quasi~peak indication for the same bandwidth. It may be convenient to measure emissions using peak detection because of the faster scan possible than with quasi~peak detection. When quasi peak limits are being used, any peak measurements close to the limit shall be measured using the quasi~peak detector.

4.5.1 Minimum Scan Time - the scan rate of a spectrum analyzer or scanning receiver shall be adjusted for the CISPR frequency band and detection mode used. The minimum sweep time/frequency (i.e., most rapid scan rate) is listed in table2:

TABLE 2 - MINIMUM SCAN TIME Band

A 9to150kHz B 0.15 to 30 MHz

C,D 30 to 1000 MHz Band definition from CISPR 16 part 1

Peak Detection Does not apply 100 ms/MHz

1 ms 1100 ms / MHzl

Quasi-Peak Detection Does not apply

200 s/MHz 20 s/MHz

IWhen 9 kHz bandwidth is used, the 100 ms 1 MHz value shall be used

Certain signals(e.g., low repetition rate or intermittent signal) may require slow scan rates or multiple scans to insure that the maximum amplitude has been measured.

4.5.2 Measuring Instrument Bandwidth - The bandwidth of the measuring instrument shall be chosen such that the noise floor is at least 6 dB lower than the limit curve. The bandwidths in table 3 are recommended.

Note - When the bandwidth of the measuring instrument exceeds the bandwidth of a narrowband signal, the measured signal amplitude will not be affected. The indicated value of impulsive broadband noise will be lower when the measuring instrument bandwidth is reduced.

81

TABLE 3 - MEASURING INSTRUMENT BANDWIDTH (6 dB) Frequency Band Broadband Broadband Narrowband Narrowband

MHz Peak q-Peak Peak Average

0.15-30 9kHz 9kHz 9kHz 9kHz 30 -1000 FM broadcast 120 kHz 120 kHz 120kHz 120 kHz

Mobile service 120 kHz 120 kHz 9kHz 9kHz

If a spectrum analyzer is used for peak measurements, the video bandwidth shall be at least three times the resolution bandwidth.

For the narrow bandlbroadband discrimination according to figurel, both bandwidths (with peak and average detectors) shall be identical.

5. Antenna and Impedance Matching Requirements - Vehicle Test

5.1 Type of Antenna - An antenna of the type to be supplied with the vehicle shall be used as the measurement antenna. Its location and attitude are determined according to the production specifications.

If no antenna is to be furnished with the vehicle (as is often the case with a mobile radio system), the antenna types in table 4 shall be used for the test. The antenna type and location shall be included in the test plan.

TABLE 4 - ANTENNA TYPES Band

Broadcast LW AM MW AM SW AM VHF FM

Mobile Services 30-54 70-87

144 -172 420-512 800 -1000

Antenna Type

Im monopole Im monopole Im monopole Im monopole

load quarter wave monopole quarter wave monopole quarter wave monopole quarter wave monopole quarter wave monopole

5.2 Measurement System Requirements

5.2.1 Broadcasting Bands - For each band, the measurement shall be made with instrumentation which has the specified characteristics.

82

5.2.1.1 AM Broadcast

a. Long Wave (150 to 300 kHz) b. Medium Wave (0.53 to 2.0 MJIz) c. Short Wave (5.9 to 6.2 MHzi

The measuring system shall have the following characteristics:

a. Output Impedance of Impedance Matching Device: 50 n resistive. b. Gain: the gain (or attenuation) of the measuring equipment shall be known with an

accuracy of ±0.5 dB. The gain of the equipment shall remain within a 6 dB envelop for each frequency band as shown in figure 2. Calibration shall be performed in accordance with Appendix I.

c. Compression Point: The 1 dB compression point shall occur at a sine wave voltage level greater than 60 dB(J.1 V)

d. Measurement System Noise Floor: The noise floor of the combined equipment including measuring instrument, matching amplifier and preamplifier (if used) shall be at least 6 dB lower than the limit level.

e. Dynamic Range: From the noise floor to the 1 dB compression point. f. Input Impedance: the impedance of the measuring system at the input of the matching

network shall be at least 10 times the open circuit impedance of the artificial antenna network in Appendix 1.

1 Gain (dB)

I

6 ~------------------------------------~ ~ow frugh

FIGURE 2 - EXAMPLE GAIN CURVE

6dB envelop

5.2.1.2 FM Broadcast (87 to 108 MHz) - Measurements shall be taken with a measuring instrument which has an input impedance of 50 n. If the standing wave ratio(SWR) is greater than 2: I, an input matching network shall be used. Appropriate correction shall be made for any attenuation/gain of the matching unit.

5.2.2 Communication Bands (30 to 1000 MHz) - The test procedure assumes a 50 n measuring instrument and a 50 n antenna in the frequency range 30 to 1000 MHz. If a measuring instrument and an antenna with differing impedances are used, an appropriate network and correction shall be used.

5 Although there are several other short wave broadcast bands, this particular band has been chosen because it is most commonly used in vehicles. It is expected that other short wave bands will be protected by conformance to the limits in this band.

83

6. Method of Measurement - As a general principle, the disturbance voltage shall be measured at the terminal of the radio receiving antenna placed at the correct vehicle location(s).

To determine the disturbance characteristics of individual disturbance sources or disturbance systems, all sources shall be forced to operate independently across their range of normal operating conditions (transient effects to be determined)

The disturbance voltage shall be measured at the receiver end of the antenna coaxial cable using the ground contact of the connector as reference. The antenna connector shall be grounded to the housing of the on - board radio (center conductor of the antenna coax is not connected to the on-board radio). The radio housing shall be grounded to the vehicle body using the production harness. The use of a high quality double shielded cable for connection to the measuring receiver is required.

NOTE The use of ferrite or other suppression material on the coax is recommended, particularly below 2 MHz, for suppression of surface current.

A coaxial bulkhead connector shall be used for connection to the measuring receiver outside the shielded room. See Figure 3.

Some vehicles may allow a receiver to be mounted in several locations (e.g., under the dash, under the seat, etc.). In these cases a test shall be carried out as specified in the test plan for each receiver location.

7. Limit for Vehicle Radiated Disturbances - The limits of disturbance may be different for each disturbance source. Long duration disturbance sources such as a heater blower motor must meet a more stringent requirement than short duration disturbance sources. Short duration disturbance may be decided upon by the vehicle manufacturer. For example, door mirror operation may be allowed at a high level of disturbance, as it is operated for only 1 or 2 s at a time. Coherent energy from microprocessors is more objectionable because it resembles desired signal and is continuous.

For acceptable radio reception in a vehicle, the disturbance voltage at the end of the antenna cable shall not exceed the values shown in table 5.

PREPARED BY THE SAE EMR STANDARDS COMMITEE

84

See 4.3

4

6

3

8

Antenna Interconnect

1. Measuring instrument 2. ALSE 3. Bulkhead connector 4. Antenna (see 5.1) 5. EUT 6. Typical absorber material 7. Antenna coaxial cable 8. High quality double shielded coaxial cable 9. Housing of on-board radio

. IO.Impedance matching unit (when required) 11. Optional tee connector with one leg removed

FIGURE 3. - VEHICLE RADIATED EMISSIONS - EXAMPLE FOR TEST LAYOUT (END VIEW WITH MONOPOLE ANTENNA)

85

1

TABLE 5. - LIMITS OF DISTURBANCE - COMPLETE VEHICLE

Tenninal noise Tenninal noise Tenninal noise Tenninal noise Voltage Voltage Voltage Voltage Tenninal noise

at Receiver at Receiver at Receiver at Receiver Voltage Antenna Tenninal Antenna Tenninal Antenna Tenninal Antenna Tenninal at Receiver

Frequency dB(J..I.V) dB{J..I.V) dB(J..I.V) dB(J..I.V) Antenna Tenninal

Band (MHz) Broadband Broadband Broadband Broadband dB(J..I.V) Continuous Continuous Short Duration Short Duration Narrowband

QP P QP P P LW 0.15 0.3 9 22 15 28 6 MW 0.53 -2 6 19 15 28 0 SW 5.9 -6.2 6 19 6 19 0

VHF 30-54 6(151) 28 15 28 0

VHF 70-87 6(15 1) 28 15 28 0

VHF 87 108 6(151) 28 15 28 6

VHF 144 - 172 6(151) 28 15 28 0

UHF 420-512 6(15 1) 28 15 28 0

UHF 800-1000 6(15 1) 28 15 28 0

All broadband values listed in this table are valid for the bandwidth specified in Table 3.

Stereo signals may be more susceptible to interference than monaural signals in the FM - broadcast band. This phenomenon has been factored into the VHF (87 to 108 MHz) limit.

It is assumed that protection of services operating on frequencies immediately below 30 MHz will most likely be provided if the limits for services above 30 MHz are observed.

ILimit for ignition system only

86

APPENDIX I (Normative)

ANTENNA MATCHING UNIT - VElllCLE TEST

1.1 Antenna Matching Unit Parameters (150 kHz to 6.2 MHz) - The requirements for the measurement equipment are defined in 5.2.1.

1.2. Antenna Matching Unit - calibration - the artificial antenna network of Figure Al is used to represent the antenna including the coaxial cable. The 60 pF capacitor represents the capacitance of the coaxial cable between the car antenna and the input of the radio.

r··········_······_··_···············_········_············_··_·····_···_--···-1 r···········_·_·················_··_·······_·····_·1

, 30 n 15 pF ! i l

50n ~=50 n "1~: I I ' 150~)

SIGNAL GENERATOR

60 pF

ARTIFICIAL ANTENNA NETWORK

ANTENNA MATCHING

UNIT

MEASURING RECENER

1.2.1 Gain Measurement - The antenna matching unit shall be measured to determine whether its gain meets the requirements of 5 .2.1.1 using the test arrangement shown in Figure A.l

1.2.2 Test Procedure

a. Set the signal generator to the starting carrier frequency with 1000 Hz, 30 % amplitude modulation and 40 dB(Jl V)output level.

b. Plot the gain curve for each frequency segnment.

1.3 Impedance Measurement - Measurement of the output impedance of the antenna and antenna matching unit shall be made with a vector impedance meter (or equivalent test equipment). The output impedance shall be within a circle on a Smith chart crossing 100 + jO n, having its center at 50 + jO n (e.g., SWR less than 2 to 1).

87

APPENDIXII (Infonnative)

NOTES ON TIIE SUPRESSION OF INTERFERENCE

n.l Introduction - Success in providing radio disturbance suppression for a vehicle requires a systematic investigation to identify sources of interference which can be heard in the loudspeaker. This interference may reach the receiver and loudspeaker in various ways:

a. Disturbance coupled to the antenna b. Disturbance coupled to the antenna cable c. Penetration into the receiver enclosure via the power supply cables d. Direct radiation into the receiver (immunity of an automobile radio to radiated

interference) e. Disturbance coupled to all other cables connected to the automobile receiver

Before the start of the investigation, the receiver housing, the antenna base, and each end of the shield of the antenna cable must be correctly grounded.

11.2 Disturbance Coupled to the Antenna - Most types of disturbances reach the receiver via the antenna. Suppressors can be fitted to the sources of disturbances to reduce these effects.

II.3 Coupling to the Antenna Cable - To minimize coupling, the antenna cable should not be routed parallel to the wiring harness or other electrical cables, and should be placed as remotely as possible from them.

HA Clock Oscillators - Radiation/conduction from on-board electronic modules may affect other components on the vehicle. Significant harmonics of the execution clock("E-Clock") must not coincide with duplex transceiver spacings, nor with receiver channel frequencies. The fundamental frequency of oscillator used in automotive modules/components shall not be an integer fraction of the duplex frequency of any mobile transceiver system in operation in the country in which the vehicle will be used

11.5. Other Sources ofInformation - Corrective measures for penetration by receiver wiring and by direct radiation are covered in other publications. Similarly, tests to evaluate the immunity of a receiver to conducted and direct radiated disturbances are also covered in other publications.

88

APPENDIXC

LIST OF FREQUENCIES USED BY TxDOT

Unit: MHz

Low Band Low Band High Band High Band High Band

45.680* 47.020 150.995 156.045 159.180

45.720* 47.040 151.010 156.060 159.225

45.800* 47.060 151.025 156.1 05 159.450

45.840* 47.080 151.040 156.120 162.400

47.100 151.055 156.135 162.475

47.120 151.070 156.180 162.550

47.140 151.085 156.195

47.160 151.100

47.180 151.115

47.200 151.130

47.220 15l.185

47.240 151.385

47.260 154.950

47.340 155.370

* Note: these frequencies used only for mobile-radio transmission to repeater and not for mobile-radio reception

89

Appendix C: IEEE Symposium Paper

Testing for FM-Radio Interference in Motor Vehicles

Thomas F. Trost, Ye Jin, Jongsin Yun, Qianlin Zhou Texas Tech University

Lubbock, TX 79409 USA

Abstract: A comparison has been carried out between two tests for predicting the effect of motor-vehicle RF emissions upon onboard FM receivers. The tests are Society of Automotive Engineers J55114, an RF peak amplitude test, and State of Texas Tex-899-B, an FM receiver SIN AD test. Tex-899-B would seem a natural choice because it employs an FM receiver like that used in the vehicle, but we have found that, by making judicious adjustments in the J551/4 limits, J55114 can also be used, and this may afford an important testing option.

INTRODUCTION

The Texas Department of Transportation (TxDOT) has found that in some cases radio interference or noise is generated by the electrical system of a new fleet vehicle at such a level that it degrades the performance of the receiver in the two-way FM radio carried in the vehicle. In response, TxDOT has developed a test method to identify offending vehicles before they are put into service. TxDOT has also initiated the project described here as an independent investigation of the problem, focusing on testing methodologies and on cooperation with the vehicle manufacturers. The first portion of the project is covered in a TxDOT report [1], and the present paper includes the results from this report plus subsequent work to date.

Two EMC test standards were of primary interest, the test used by TxDOT and referred to above, Tex-899-B [2], and a Society of Automotive Engineers test, SAE 155114 [3]. Both tests place limits on RF emissions. Tex-899-B specifies an RF emissions limit, indirectly, as the amount of noise that produces a 12 dB SINAD value [4] in the output of a TxDOT radio when an FM signal is present. J55114 specifies direct limits on peak RF emissions for narrowband sources and for broadband sources. By design, Tex-899-B is well suited to uncovering potential TxDOT interference problems; but the applicability of 1551/4 to the TxDOT situation was not known a priori.

OBJECTIVES AND ApPROACH

Our objectives were to assess the degree of correlation between the two tests and to determine whether some modified form of the 155114 test could be found that would be as effective as Tex-899-B and that the automakers would be willing to perform to qualify their vehicles for TxDOT service. J551/4 seemed like a better candidate than Tex-899-B for use by the automakers primarily because it appeared to be less time-consuming to carry out.

1

The range of frequencies where the TxDOT radios operate lies in the two-way radio low-band VHF range and extends from 47.02 MHz to 47.34 MHz. However our approach and our results are valid for automotive interference to wide-band FM radios operating at any frequency.

Our approach involved a two-pronged attack on the problem. First, we performed the 1551/4 and Tex-899-B tests outdoors on a number of TxDOT vehicles. This work provided insight into the nature of the emissions produced. Second, we performed bench-top tests related to 155114 and Tex-899-B on several TxDOT radios. Ten different types of RF noise sources were employed, including laboratory waveform generators simulating vehicle sources and actual vehicle components such as electric fuel pumps. This work gave us a chance to vary noise amplitudes and examine the effects on the radios.

VEHICLE TESTS

The test-equipment setup for the whole-vehicle tests was straightforward. For Tex-899-B, a magnetic-mount whip antenna was located on the vehicle roof and coupled, along with an FM signal generator, through a directional coupler to a TxDOT radio. The audio output of the radio was fed to a SINAD meter. For J55l/4, the same antenna was connected instead to a CISPR-compliant EMI receiver (Rohde & Schwarz Model ESS) [5].

The test procedure was as follows: Vehicle electrical components that were potential noise sources were switched on and off. For the Tex-899-B test, while each component remained on, the FM signal amplitude required to achieve a 12 dB SINAD was noted. The specified limit is 0 dBJ.tV, and the modulation is to have a frequency of 1.0 kHz and a frequency deviation of 3.3 kHz. For the 1551/4 test, the peak noise reading on the EMI receiver was noted. The specified limits are 0 dBJ.tV for narrowband and 28 dBJ.tV for broadband noise, and the measurement bandwidths to be used are 9 kHz and 120 kHz, respectively.

The vehicles consisted of four Chevrolet, six Dodge, and three Ford pickup trucks. All had engines powered by gasoline or by gasoline and propane; and all were 1997 models, except for one of the Dodges which was a '96. Most of the trucks were tested by Southwest Research Institute in San Antonio [6,7], but some were tested by Texas Tech University at a field site near Lubbock and some by Professional Testing, Inc. at a site near Marble Falls, TX.

The three main sources of noise at low-band VHF were found to be the spark-ignition system, DC motors such as those in fuel pumps and HV AC fans, and electronic modules. The bandwidth of the spark-ignition and DC-motor noise is large, extending across the TxDOT range of frequencies. This is broadband noise. The bandwidth of the module noise is narrow, less than or comparable to the 15 kHz bandwidth of a TxDOT radio. This is narrowband noise. A discussion of the whole-vehicle test data is given below under Test Results and Analysis. A detailed presentation of the data is contained in [1].

BENCH TESTS

Our bench-top tests were conducted at Texas Tech University on five radio models, but concentrated on just two, the GE RANGRTM and the Motorola MaraTrac, which are the primary radios in the TxDOT fleet. A block diagram of the test-equipment setup is shown in Figure 1. The lines connecting the blocks represent coaxial cables. The noise sources are connected individually to the hybrid junction, which combines the noise and the FM signal and sends the combination to both the FM radio and the EMI receiver (Rohde & Schwarz Model ESS).

NOISE SOURCES

• • •

FM SIGNAL GENERATOR

HYBRID JUNCTION

EMI RECEIVER

SINAD METER

FM RADIO UNDER TEST

Figure 1. Block Diagram of Bench-Top Test System

The measurement procedure used with this setup contained a Tex-899-B component and a J55114 component, thus allowing a comparison of the two test techniques for each radio. The procedure was as follows: (1) The FM signal was set to 0 dBJlV, which is the Tex-899-B limit. (2) With a particular noise source connected, the noise amplitude was adjusted to produce a SINAD reading equal to 12 dB, which is the value used in Tex-899-B. (3) The FM signal was switched off and the amplitude of the noise was measured with the EMI receiver, as in the J551/4 test, thus giving the J55114 value corresponding to the Tex-899-B limit.

2

Results show that the radios are very sensitive to narrowband noise but not to broadband. The radio IF noise blanker circuits are highly effective at removing the large, narrow pulses which are the basis of the broad band noise. A discussion of the bench-top test data is given below under Test Results and Analysis. A detailed presentation of the data is contained in [I].

TEST RESULTS AND ANALYSIS

Narrowband Emissions

Narrowband noise emissions were not found in the TxDOT frequency range (47.02 - 47.34 MHz) on the thirteen vehicles tested, although some were detected nearby at about 48 MHz.

The value needed for the J55114 narrowband limit in order to achieve good correlation between the two tests was inferred from the bench test data. The resulting value is - 3 dBJlV. It was obtained using a CW noise source and a MaraTrac radio, which is the newer of the two primary TxDOT radios. Thus the current J55114 limit of 0 dBJlV must be lowered a bit for application to the TxDOT situation. This result is not surprising since the maximum FM signal used in the Tex-899-B test (the Tex-899-B limit) has the same value, 0 dBJlV; and the radios cannot tolerate an amount of noise that is equal to the amount of signal. That is, an FM detector requires that an interfering signal be at least a few dB below the desired signal for good reception [8].

Broadband Emissions

Broadband emissions were observed on the vehicles and were of such an amplitude as to cause the vehicles to pass the Tex-899-B test but to fail the J55114 test. The emissions were due to DC motors and spark ignition. For the J55114 measurements using the EMI receiver with 120 kHz bandwidth, the maximum DC-motor noise among all the vehicles was found to be 37 dBJlV peak, and the maximum spark-ignition noise was 56 dBJlV peak. Thus the current J55114 limit of 28 dBJlV must be increased to bring J55114 into agreement with Tex-899-B.

Information on the required amount of increase comes from the bench test data. Here a slight complication is encountered, as it is found that a separate limit is needed for each kind of broadband noise. The reason for this is that not only the radios' FM detectors but also their noise blankers come into play, and the noise blankers are less effective against DC­motor noise than against spark-ignition noise. For DC-motor noise, the modified limit turns out to be 40 dBJlV peak. This value applies to the MaraTrac radio, being slightly lower for the RANGRTM. It comes from a bench test where a fuel pump, an HV AC fan, and a radiator fan were employed simultaneously as the noise source. The noise was coupled from the battery leads with a current transformer and connected to the hybrid junction (Figure 1) through an attenuator. There is an inherent randomness to DC-motor

noise which gives the limit a statistical nature. Even for a long, two second, measurement time, we observed a 2 dB standard deviation in the peak noise readings.

For spark-ignition noise, the modified limit is very high. We used a laboratory pulse generator to simulate spark-ignition noise and applied up to 88 dB/-iV peak in a 120 kHz bandwidth to a TxDOT radio but still could not reduce the SIN AD value below 28 dB, well above the required 12 dB value. The simulated noise consists of short, ringing pulses with low repetition rate (about 100 ns duration at 50 pps), and the radios display a refractory behavior to this kind of input. The maximum amplitude applied in these bench tests, 88 dBJ.l.V, measures 11 V peak-to-peak and is more than 30 dB above the highest value we observed in our vehicle tests. So it appears that although we do not know the value of the limit exactly, it is high enough that spark-ignition noise is not a threat to the radios, for the current generation of TxDOT trucks at least.

Combined Emissions

To test the radios' response to a combination of narrowband and broadband emissions we connected two of the bench-top noise sources in Figure 1 through a directional coupler to the hybrid junction. We used a CW source for narrowband and an HV AC fan for broadband and varied the relative amplitudes of the two while maintaining a 12 dB SINAD value on the radio (with 0 dB/-iV FM signal). The results are given in Figure 2 for a MaraTrac radio.

60

... ....G > ::1. 50

CC ~

<1> "0

.~ 40 a. E «

~ - -.......... r--~ V ~

'"

~ .... .... .... ....

i~ ::.! co 30 <1>

0...

ro 1\

<1> <n Ir ·0 Z 20 c co LL () « 10 > I

0

~ ~ 1-

~ "\ -8 -7 -6 -5 -4 -3 -2

cw Noise Peak Amplitude (dBJ.l.V)

Figure 2. Comparison of Tex-899-B and Modified J551/4 Limits for a Combination of Narrowband and Broadband Noise

3

The same test was carried out three times to check repeatability, resulting in the three curves shown. The interpretation of these curves is that they mark the location of the Tex-899-B limit as a function of the amplitudes of the two noise sources. The horizontal and vertical lines drawn at 40 dB/-iV and -3 dB J.l.V , respectively, give the location of our modified J55114 limits. Hence the degree of correlation between the limits of the two tests can be visualized.

One might be inclined to argue that our 40 dBJ.l.V limit line in Figure 2 lies well below the left end of the curves and as such is too conservative. But, as a final step, the curves must be adjusted for the worst case in a vehicle, which means running a fuel pump and a radiator fan in addition to the HV AC fan, as mentioned above under Broadband Emissions. Our bench tests show that if two or three motors are running instead of just one, the radios are more strongly affected, and the curves in Figure 2 are displaced downward toward 40 dB/-iV. This will produce better agreement between the limits at the left end, although it will degrade somewhat the good agreement seen on the right at the knee of the curves.

Modified }55114 Test

Shown in Table 1 is a suggested test plan for a J551/4-type test tailored to TxDOT needs. It contains the modified limits discussed above and also includes ambient limits, which are set 6 dB lower. The frequency range for the measurements is 46.9 MHz to 47.4 MHz, giving a slightly broader view than just the TxDOT range itself. Peak detection is to be used with a measurement time (or sweep time if using a spectrum analyzer) of2 s.

All the limits in Table 1 were chosen to correspond to the limit of the Tex-899-B SINAD test conducted with a Motorola MaraTrac radio. A changeover to some other radio by TxDOT in the future might require adjustments to these limits.

Carrying out the test in Table 1 has advantages and disadvantages compared to carrying out Tex-899-B. The advantages stem from the use of an EMI receiver (or spectrum analyzer), as compared to a TxDOT radio, FM signal generator, and SINAD meter. With the receiver, the equipment setup is simpler; and, unlike the TxDOT radio, the EMI receiver is a common piece of calibrated laboratory instrumentation and one which admits computer control. The receiver also allows one to check not only the TxDOT frequencies for narrowband noise but also those frequencies in between and on either side. In this way, narrowband emissions that do not at the moment lie on a TxDOT frequency, but which are drifting and thus pose a potential threat, can be identified. On the other hand a disadvantage of the test in Table 1 is that, if new sources of RF noise arise in future vehicles and new TxDOT radios come into service, the Tex-899-B test will take these changes into account by simply changing to the new radio, while the modified 1551/4 limits in Table 1 will have to be re-evaluated for the new situation.

Table 1. Modified J55114 RF-Emissions Test for New TxDOT Vehicles

Test Configuration

Measurement Limit Comment Bandwidth (kHz) (dB)lV)

1. Run engine until warm 2. All OFF 3. All OFF 4. Engine OFF, key ON

9 120

9

5. Engine OFF, key ON, fuel pump, 120 wipers, and HV AC fan ON (and radiator fan ON, if electric)

Furthermore, the Table 1 test is fundamentally a less direct measure than Tex-899-B of the performance of FM radios in TxDOT vehicles.

CONCLUSIONS

Although the degree of correlation between the tests Tex-899-Band J551/4, with the original J551/4 limits, is poor, a series of changes in the J55114 limits, as recommended here, would improve the correlation and allow J55114 to be substituted for Tex-899-B. In addition, the EMI receiver or spectrum analyzer used with J551/4 provides testing flexibility unavailable from a TxDOT radio, such as fast measurements on many frequencies and computer control. If one can put up with a less direct method of predicting vehicle performance in the TxDOT setting, the modified J551/4 appears be an attractive alternative to Tex-899-B.

ACKNOWLEDGMENTS

This project was supported by the Texas Department of Transportation through Contracts 7-2995 and 7-4936. The project director was Don Lewis.

The EMI receiver, an RF signal generator, and a SINAD meter used extensively in this project were supplied by Rohde & Schwarz GmbH & Co. KG and Tektronix, Inc.

Valuable suggestions were contributed by B. Rehm of Professional Testing, Inc. and D. Mehrl of Texas Tech University. Research assistance was provided by Prasanna Bahukudumbi and Chad Bonner.

REFERENCES

[I] T. F. Trost, "Testing for FM-Radio Interference in Motor Vehicles," final report on Research Project 7-2995, Texas Department of Transportation, Austin, TX. December, 1998.

[2) Test Method Tex-899-B, "Radio Frequency Interference (RFI) Testing," Texas Department of Transportation, Austin, TX,1995.

4

-9 34 -3

40

Ambient Ambient Look for narrow band microcontroller emissions Look for broad band DC­motor emissions

[3] Surface Vehicle Standard SAE J551/4, "Test Limits and Methods of Measurement of Radio Disturbance Characteristics of Vehicles and Devices, Broadband and Narrowband, 150 kHz to 1000 MHz," Society of Automotive Engineers, Warrendale, PA, 1994.

[4] TIAlEIA Standard TIAlEIA-603, "Land Mobile FM or PM Communications Equipment Measurement and Performance Standards," Telecommunications Industry Association, Washington, DC, February, 1993.

[5] CISPR 16-1, "Specification for radio disturbance and immunity measuring apparatus and methods, Part I: Radio disturbance and immunity measuring apparatus." 1993, International Electrotechnical Commission, Geneva, Switzerland.

[6] J.J. Polonis and R.W. Thompson, "Evaluation of Whole­Vehicle Radiated Emissions Test Methods for Mobile Radio Performance," report on Project 10-8766, Southwest Research Institute, July 16, 1997.

[7] J.B. Scrivner and D.A. Smith, "A Development of Guidelines for Control of Radio Frequency Interference (RFI) in Vehicles," report number EMCR 98/075 on Project 10-1548-001, Southwest Research Institute, September. 1998.

[8] M. Schwartz, et al., Communication Systems and Techniques, IEEE Press, 1996.

Appendix D: MSEE Thesis by Prasanna Bahukudumbi

CHARACTERIZATION OF MOTOR VEHICLE RADIO

INTERFERENCE USING AVERAGING DETECTORS

by

PRASANNA V. BAHUKUDUMBI, B.E.

A THESIS

IN

ELECTRICAL ENGINEERING

Submitted to the Graduate Faculty of Texas Tech University in

Partial Fulfillment of the Requirements for

the Degree of

MASTER OF SCIENCE

IN

ELECTRICAL ENGINEERING

Approved

~L;;;r Chairperson of the Committee

December, 2000

ACKNOWLEDGEMENTS

I would like to thank my family for their continuous support. I would like to

thank Dr. Trost for his patience and guidance. His determination helped me to see

through the problems and emerge successfully. His continuous assistance and

involvement in the project made this possible. I would like to thank Dr. Krile for his

persistence. I salute his amazing computing skill that helped me to back up my

experimental findings with theoretical proof. I would like to thank Dr. Mehrl for his

guidance, which helped me to proceed on my project with better thought.

I would like to extend my thanks to Mr.Yun who helped me with all my

measurements and documentation. Finally, I would like to thank the people at the Texas

Tech motor pool and the people of TxDOT whose cooperation helped me to complete the

project.

11

T ABLE OF CONTENTS

ACKNOWLEDGEMENTS ....................................................................... .ii

ABSTRACT ........................................................................................... v

LIST OFTABLES ................................................................................... vi

LIST OF FIGURES ................................................................................ viii

I. INTRODUCTION .............................................. , .................................. 1

1.1 Standard units used in measurements ..................................................... 2

1.2. Problems in vehicles ........................................................................ 3

IT. EVALUATION OF HP E740lA EMC ANALYZER ......................................... 5

2.1. Internal noise level comparison ........................................................... 5

2.2. Narrow-band comparison .................................................................. 6

2.3. Broadband comparison ............. '" ................................................... 7

2.4. Comparison of filter shapes .............................................................. 8

2.5. Comparison of average measurements ................................................ 10

2.6. Noise emissions from the ESVP and E740IA ....................................... 15

2.7. Summary .... , .............................................................................. 15

rn. Tex-899-B TEST ............................................................................... 16

3.1. TxDOT Dodge trucks 2-5643-0 and 2-5649-0 ...................................... 16

3.2. Texas Tech University Dodge truck .................................................... 21

3.3. Texas Tech University Chevrolet truck ............................................... .23

3.4. Texas Tech University Ford truck ...................................................... 25

ii i

IV. J551/4 TEST ..................................................................................... 27

4.1. TxDOT Dodge trucks 2-5649-G & 2-5643-G ......................................... 27

4.2. Texas Tech University Dodge truck ................................................... .31

4.3. Texas Tech University Chevrolet truck ................................................ 34

4.4. Texas Tech University Ford truck ..................................................... .35

V. AVERAGE MEASUREMENTS ............................................................. 38

5.1. Computation of theoretical peak-to-average ratio .................................. Al

5.2. Broadband micro-controller noise .................................................... .42

5.3. A verage limit for DC motor noise .................................................... .46

5.4. Comprehensive test procedure ......................................................... .47

VI. CONCLUSIONS ............................................................................... 49

6.1. Future research ........................................................................... 51

REFERENCES ..................................................................................... 52

APPENDICIES

A. TxDOT Tex-899-B TEST ................................................................... 54

B. SAE J551/4 TEST ............................................................................. 61

C. MA1LAB PROGRAM FOR CALCULATION OF THEORETICAL PEAK-TO-A VERAGE ........................................................................ 74

IV

ABSTRACT

This research examined two different testing procedures for measuring the

electromagnetic interference in a communication receiver in a motor vehicle. The

procedures were analyzed, compared, and their differences were examined. The research

found that by modifying one of the test procedures, the agreement between the two was

improved.

The research also revealed the usefulness of an average detector in the estimation

of one type of noise in the presence of other types. This led to development of a

prototype of an auxiliary testing procedure. The prototype procedure takes advantage of

a reduction in the ambient noise level in outdoor tests. This prototype gave good results

when used in both laboratory and practical vehicle tests.

v

LIST OF TABLES

2.1. Internal noise levels ofESVP receiver and E7401A analyzer. ........................... 6

2.2. Measurement settings on the receiver and the analyzer.. .................................. 6

2.3. Comparison of the receiver and the analyzer for a CW signal input.. ........................ 7

2.4. Comparison of the peak measurement for a pulse source ................................. 9

2.5. Measured peak values at 9/10 kHz bandwidth ............................................. 11

2.6. Measures average values at 9/10 kHz bandwidth .......................................... 11

2.7. Measured peak values at 120 kHz bandwidth .............................................. 13

2.8. Measured average values at 120 kHz bandwidth ........................................... 13

3.1. Mode number and its respective center frequency, TxDOT trucks ...................... 17

3.2. Ambient noise levels ........................................................................... 18

3.3. Summary of Tex-899-B test on the Dodge truck from TxDOT (2-5649-0) ........... 19

3.4. Summary of Tex-899-B test on the Dodge truck from TxDOT (2-5643-0) ........... 20

3.5. Mode number and its respective center frequency, TIU trucks ......................... 21

3.6. Ambient noise levels ........................................................................... 22

3.7 Summary of Tex-899-B test on the Dodge truck from Texas Tech ..................... 22

3.8. Tex-899-B key-on test for other frequencies ................................................ 23

3.9. Ambient noise levels ........................................................................... 24

3.10 Summary of Tex-899-B test on the Chevrolet truck from Texas Tech .................... 24

3.11. Ambient noise levels ......................................................................... 25

3.12 Summary of Tex-899-B test on the Ford truck from Texas Tech ....................... 25

VI

4.1. Noise level of EMI receiver at 47.18 MHz ................................................. 27

4.2 Ambient noise levels at 47.18 MHz .......................................................... 28

4.3. Summary of J551/4 test on TxDOT truck (2-5649-0) .................................... 28

4.4. Summary of J551/4 test on TxDOT truck (2-5643-0) .................................... 30

4.5. Ambient noise levels (Pre-amp ON) ......................................................... 32

4.6. Summary of J551/4 test on Dodge truck from Texas Tech .............................. 32

4.7. Ambient noise levels ........................................................................... 34

4.8. Summary of J55114 test for Chevrolet truck from Texas Tech ........................... 34

4.9. Ambient noise levels ........................................................................... 36

4.10. Summary of J55114 test on Ford truck from Texas Tech .............................. 36

5.1. Peak and average for DC motors for 12 dB SINAD using ESVP receiver. ........... .46

5.2. Peak and average for DC motors for 12 dB SINAD using HP analyzer. .............. .47

Vll

LIST OF FIGURES

2.1. Comparison of filter shapes for BW = 9110 kHz ...................................... 9

2.2. Comparison of filter shapes for BW = 120 kHz ..................................... 10

2.3. Comparison of different averaging techniques (9110 kHz) ........................ 12

2.4. Comparison of different averaging techniques (120 kHz) ......................... 14

4.1. Narrow-band key-on scan from TxDOT Dodge truck 5649 G .................... 29

4.2. Narrow-band key-on scan from TxDOT Dodge truck 5643 G .................... 31

4.3. Key-on noise from Texas Tech Dodge truck ........................................ 33

4.4. Key-on and ambient noise on the Chevrolet truck .................................. 35

5.1. Comparison of various detectors used for EMI measurements ................... 38

5.2. Comparison of different detectors to separate different noise sources .......... .40

5.3. Micro-controller noise at different instances ....................................... .43

5.4. Peak and average plot of the micro-controller noise .............................. .44

5.5 Comparison of peak and average noise amplitude with 12-dB SINAD signal amplitude ...................................................................................... 45

6.1. Comparison of peak, average and SINAD values of different trucks .............. 50

V1l1

CHAPTER I

INTRODUCTION

The last decade has shown a marked increase in the use of electronic products,

which has also increased concern about electromagnetic interference. Electromagnetic

Interference (EMI) is any electromagnetic disturbance that degrades the performance of

any electronic equipment. The electronic industries are trying to minimize the

interference problems by using suitable design measures [1, 2,3]. These industries have to

produce electromagnetically compatible equipment to comply with the standards imposed

by the government and to satisfy their customers. Organizations like the FCC [4], SAE

[5J, and CISPR [6] monitor product performance to maintain certain standards.

EM! testing is classified into four categories. These categories test various

possibilities in both the control of emissions from the equipment and control of

susceptibility of the equipment [3]:

1. Radiated emissions (RE),

2. Radiated susceptibility (RS),

3. Conducted emissions (CE), and

4. Conducted susceptibility (CS).

The radiated emissions test is used to measure the emissions radiated from the

equipment and check it against a pre-defined limit set by the regulatory board. The

radiated susceptibility test is used to measure the immunity of the equipment against

radiated emissions from other electronic products. The remaining two categories are the

same as the above except that they involve conducted phenomenon.

There are numerous sources that contribute to interference. They can be classified

as natural and man-made. Some man-made interference sources are switching transients,

DC motors, spark noise from ignition systems and harmonics of the clocks that are used

in micro-controllers. Switching transients and ignition noise affect a huge spectrum

because of their many spectral components.

1.1 Standard units used in measurements

The amplitude units used for the measurement of EM! are usually variants of the

decibel [3]. The commonly used units are the dBm and dBJ.LV. The unit dBm is the ratio

of power with reference to ImW:

dBm = 10 10glO [signal strength (mW) IlmW].

The unit dBJ.LV is a ratio of voltage with reference to IJ..1.V:

dBJ..I.V = 20 10glO [signal strength (J..I.V) IIJ..l.V].

These units are related by the following expression in a 50-ohm EM! measurement

system:

o dBm = 107 dBJ..I.V.

The signals received as input to the receiver will be in the range of IJ..1.V so these

units suit the measurement range. Other less popular units are dBJ..I.VIMHz and dBJ..I.A [3].

2

1.2 Problems in vehicles

Nowadays automobiles contain a lot of electronic/electric equipment. Sometimes

one piece of equipment causes significant interference to another. The main interference

sources for a communication receiver in an automobile [7,8] are the following:

1. Spark ignition noise produced from the spark plug. This noise is impulsive and

extends across many MHz.

2. DC motor noise (from motors like fuel pump, HV AC fan, light bar, wipers and

washer motors, etc.). This noise is due to the sparks produced at the brushes of motors.

3. Micro-controller noise. This noise is primarily due to the clocks and their

harmonics.

These noise sources contribute to broadband and narrow-band noise. The

communication receiver reacts differently to each. There are two standard testing

procedures available for testing a communication receiver in a vehicle for

electromagnetic interference:

1. Tex-899-B proposed by the Texas Department of Transportation (TxDOT) to

test the two-way radios installed in their trucks. It has been recently renamed as Tex-

1160-T (Appendix A).

2. J551 proposed by SAE (Society of Automobile Engineers) to test any

communication receiver installed in a motor vehicle. Major vehicle manufacturers in the

US use the J551 test (Appendix B).

These standards are used to quantify, and set limits on, the emissions from

vehicles. They have different procedures and different results for the same

3

communication receiver in the same automobile. This thesis intends to propose some

changes, which wil1 bring some agreement between the two standards. There are also

proposals for an auxiliary testing procedure to test for interference in automobiles along

with the 1551 tests. The forthcoming chapters discuss the calibration tests made to assert

the accuracy of the two test instruments used (Rohde & Schwarz EMI receiver and HP

EMC analyzer), the standard testing procedures and their results, and then the use of

average-detector measurements, the auxiliary testing procedure, and a comparison with

the existing procedures. In arriving at the results, several trucks belonging to TxDOT

were tested.

4

CHAPTERIJ

EVALUATION OFHPE740lA EMC ANALYZER

The first step in EMI measurement is calibration and testing the accuracy of the

instrument to be used with a standard instrument. In this chapter an HP E740lA analyzer

is compared with a Rohde& Schwarz ESVP receiver as the standard. The ESVP receiver

has a CAL button which when pressed for 3 seconds calibrates the receiver with an

internal generator as a reference [9]. The HP E740IA is a new product on the market, and

it has both the features of an EMI receiver and a spectrum analyzer, i.e., the measurement

capabilities of the receiver and the visual representation of the spectrum analyzer.

There are several new features in this analyzer, which make it suitable for pre­

compliance tests. The limit disk gives the limits for the EMI testing for several

applications [10]. The analyzer determines the result of a measurement based on the limit

and displays pass or fail. The limits can be changed and corrections can also be added for

different types of antenna and loads to minimize error in the measurement [11]. This

analyzer has all the detectors of an EMI receiver (peak, quasi-peak and average). It has an

internal memory to store waveforms, screens, traces and states. It runs on a 12 V battery,

which makes it ideal for open area testing. The analyzer is much cheaper than the EMI

receiver.

5

2.1 Internal noise level comparison

The internal noise levels of both the receiver and the analyzer were measured and

listed in Table 2.1. The center frequency was 47.18 MHz and the RF attenuation was 0

dB.

Table 2.1: Internal noise levels of ESVP receiver and E7401A analyzer

Pre-amp ON Pre-amp OFF

BW=120 kHz BW=9kHz BW=120kHz BW=9kHz

ESVP 0 -J 1.5 9.5 -2.1

Peak (dBIlV)

ESVP 12.3 -23.5 -4.6 -15.7

Average (dBIlV)

E7401A Peak -0.2 -13.8 16.5 3.1

(dBIlV)

E7401A Average -10.8 -22.3 2.9 -8.5

(dBIlV)

It is found that, with the pre-amp switched on, the noise level of the E7401A

analyzer becomes comparable to that of the ESVP receiver.

2.2 Narrow-band comparison

Noise sources are divided into narrow-band and broadband. A comparison was

done for each and the results were tabulated. The narrow-band comparison was

conducted using a Fluke 6060B signal generator as a CW source at 47.18 MHz. Table 2.2

gives the receiver and analyzer settings, and Table 2.3 gives a comparison of their

measured values for the CW signal using a sine-wave source. Table 2.3 also compares

6

both conditions of pre-amp ON and OFF, so it is also used to detennine the effect of the

pre-amp on narrow-band signals.

Table 2.2: Measurement setting on the receiver and the analyzer

ESVP HPE7401A Attenuation o dB (Auto o dB (Auto

attenuation ON) attenuation ON) Bandwidth 10 kHz 9 kHz (span 0 Hz) Sweep Time/ 2 sec 2 sec

Measurement Time

The table shows good agreement for a peak measurement between the receivers

and the source at strong signal levels (-90 to -30 dBm). The agreement in the peak

measurement improves when the pre-amplifier is on at low signal levels (-120 to -100

dBm). The dynamic range in the case of the ESVP can be chosen from one of the three

available ranges (20, 40 and 60 dB). We can see that at low signal levels the measured

value is limited by the internal noise of the receivers.

T bl 23 C a e f h ompanson 0 t e receIver an d h f t e ana yzer or a CW· I· sIgna mput Source Pre-amp ON (dBm) Pre-amp OFF (dBm) (dBm)

ESVP E7401A ESVP E7401A Peak Avg Peak Avg Peak Avg Peak Avg

-30 -30.2 -30.5 -30.65 -30.72 -30.4 -30.5 -30.47 -30.38 -40 -40.5 -40.5 -40.71 -40.67 -40.3 -40.5 -40.43 -40.31 -50 -50.3 -50.6 -50.67 -50.61 -50.1 -50.5 -50.35 -50.21 -60 -60.5 -60.2 -60.71 -60.46 -60.5 -60.2 -60.2 -60.17 -70 -70.2 -70.2 -70.46 -70.35 -70.3 -70.5 -70.13 -70.15 -80 -80.5 -80.6 -80.29 -80.3 -80.1 -80.5 -79.87 -80.13 -90 -90.2 -90.5 -89.86 -90.3 -89.97 -90.3 -89.2 -90.17 -100 -99.6 -100.6 -99.6 -100.3 -98.1 -100.5 -97.8 -100.2 -110 -107.9 -110.7 -107.8 -110.4 -103.9 -110.3 -101.9 -109.9 -120 -113.3 -120.4 -115.2 -120.3 -108.8 -118.8 -105.4 -114.6

7

2.3 Broadband comparison

The broadband source used for the receiver-analyzer comparison was an EH 139B

pulse generator. It was set for a pulse width of 10 ns and a repetition rate of 1500 pps.

The bandwidth of the receiver and analyzer was changed to 120 kHz. Other settings

remained the same as the narrow-band settings.

Table 2.4: Comparison of the peak measurement for a pulse source

E7401A (dBp'v) ESVP(dBp'v) E7401A (dBJ,tV)

Pre amp OFF PreampON

15.62 9.5(Pre amp ON) 10.7

20.2 18.6 18.9

25.3 24.5 24.7

34.5 33.7 33.3

43.5 42.9 39.2

54.4 53.8 37.5

64.1 64.7 41.1

From Table 2.4, the E7401A with pre-amp OFF has higher peak values than the

ESVP. The pre-amp had to be switched on for the 9.5 dBJ-tV measured on the ESVP

because it was close to the noise level (refer to Table 2.1). The rest of the measurements

taken using the ESVP had the pre-amp OFF. The pre-amp of the HP seems to saturate

around 34 dBJ-tV. This seems to be a limiting factor with the HP analyzer because usually

the pre-amp is switched on during measurements on vehicles, where the signal varies

widely from a couple of dB to several of tens of dB.

8

2.4 Comparison of filter shapes

Using a fixed source and varying the center frequency of the receivers the filter

shapes of the receiver and analyzer were determined. The input amplitude of the signal

generator was set at -70 dBm and the frequency at 47.18 MHz. The center frequency of

the receivers was changed in steps of 1 kHz.

From Figures 2.1 and 2.2, it is evident that the filter shapes of the receiver and

analyzer are different. The ESVP has a filter with very low skirts. The filters are designed

based on the CISPR specification [12], and it is evident that both filters satisfy these

specifications. However the ESVP has a higher rejection level outside the pass band and

so a better filter shape than the E7401A.

-50

i --¥-- E7401A

i ~ ESVP -60 ········································i·········· .. · ............................•........................ -'-0-- CISPR LOWER LIMIT I i ---- C IS P R H I~ HER L IM IT

-70 ~~~~ .... ~ ........ =t ................................................. ; ................... _ .................. . f ,

, E i [!) "0

·······················_····1···············_········· ............. .

CD "0 i ::J

c. -90 .E <t

.................................. ····f·····Jt······························t··········· .................... t·····I··· ····································1················· ............ __ ...... .

i i ~ ~ -100 ...................................... ! ......................................... ! .......................................... ~...... . ... -.......................... ~ ....................................... .

-110 -----l-----I----I-------f-------47.17 47.175 47.18 47.185 47.19 47.195

Frequency M Hz--->

Figure 2.1: Comparison of filter shapes for BW = 9110 kHz

9

-50

----+- E7401A -55 ESVP

CISPR LOWER LIMIT -60 !-..... , ......................................................................... ·, ....... · ...... · .... · .... · .. ,H _'" CISPR HIGHER LIMIT ..

-65

~ -70 . 1-........................ + .............. , ......... +",+ .... " ....... " .... : .. A.~. : 'A. .. "'" ............ t· .............. ,,· .... · .. + .. · ...... · ............ ·+ .. ··, .. · .... ··· ........ -j

E ID "Cl

-75 ID

"Cl ::J

a. -80 E «

-85

-90

-95

<fi~' '~

~~(i) .'~~

........................... '/ ......... _" .. _." .. _ ... u-r.,} f-1--~."';'\ ................................................. -1

----- t-----} ,> c \ • "

............ ·· ...... · .. 1 ...... · .......... ·...... ~

-100~----~----~----~----~----~------~----~--~

47 47.05 47.1 47.15 47.2 47.25 47.3 47.35 47.4

Frequency M Hz --->

Figure 2.2: Comparison of filter shapes for BW = 120 kHz

2.5 Comparison of average measurements

The receiver and the analyzer employ average detectors which, unfortunately,

display a somewhat non-ideal behavior. The ESVP has an average detector that in some

cases gives different results for different operating ranges (20,40 and 60 dB). The

E740lA has an average detector that gives different results when the pre-amp is switched

on. It also has another averaging technique called video averaging. In this kind of

averaging the analyzer changes its mode to sample detect, and it averages the amplitudes

at particular frequencies for a specific number of scans set by the user. The trace obtained

as a result is essentially the geometric average amplitude. The EH 139B pulse generator

10

was used for comparing average detectors. The pulse repetition rate was varied while the

amplitude and the pulse width were fixed. The pulse width was 10 ns and amplitude was

38.5 dBJLV at 47.18 MHz.

Table 2.5: Measured peak values at 9/10 kHz bandwidth

ESVP ESVP ESVP E7401A E7401A 20 dB range 40 dB range 60 dB range Pre-amp OFF Pre-amp ON (dBJLV) (dBJLV) (dBJLV) (dBJLV) (dBJLV) 38.5 38 38.5 39 27

Tables 2.5 and 2.6 show the measured peak and average values. These are used to

plot a peak-to-average ratio graph for comparison with theoretically calculated peak-to-

average values (refer to Chapter V, section 1). It is found that the HP peak with the pre-

amp ON has a different value which is around 11 dB less than all other peaks. That effect

is mainly due to saturation of the pre-amplifier. V A in Table 2.6 means video averaging.

Table 2.6: Measured average values at 9/10 kHz bandwidth

Repetition ESVP ESVP ESVP HP HP HP Rate (Hz) 20 dB 40 dB 60 dB Pre-amp Pre-amp VA

range range range OFF ON Pre-amp (dBJLV) (dBJLV) (dBJLV) (dBJLV) (dBJLV) OFF

(dBJLV)

50 -12.5 -19.2 -19.2 -4.11 -20.5 -8.7 100 -8 -15.8 -15.4 -1.02 -20.1 -5.6 500 17.2 8.1 10.2 10.7 -13.85 -4.5 1000 19 18.8 18.9 17.16 -8.45 10.5 2000 28.7 28.5 28.5 22.7 -4.88 16.89 3000 29.6 29.5 29.5 26.7 -0.34 25.6 4000 33.1 32.9 32.9 28.87 2.77 25.6 5000 34.1 34 33.5 31.3 4.787 28.5 7000 35 35.8 36.1 33.54 7.1 32.9 10000 37.2 37.1 37.2 35.39 8.5 32.8

11

Figure 2.3 shows a graph of all the peak-to-average ratios.

60r---------------~----------------~--------------__,

50~·· .. ··········· ............ · .. ·· ...... ·· ...... "~~ ...... · .... ·i .... "~,· ............................................................ + ...................................................................... ~

40 ............................................ .

.................................................................... '1" ............ .. C 30 <J.)

E ~ :::l .................................................................... '1" ............................................ .

---+- ESVP 20 dB

(j) 20 t1! <J.)

E <J.) 10 0)

r:! ESVP 40 dB

-B- ESVP 60 dB

HP pre-amp on

--t-- HP pre-amp off

~ t1! 0

~ .::.:. t1!

-10 ID a.

---v- Hp video averaging

-20 -A- Theoretic al

-30~--------------~----------------~--------------~

101

Repition rate (Hz)

Figure 2.3: Comparison of different averaging techniques (9/10 kHz)

From the graph, it looks like the measurements from the ESVP fit the theoretical

curve after 1 kHz. The ESVP readings (40 and 60 dB) for 50 Hz are approximately 4 dB

above the noise level so it may not be accurate. The HP pre-amp OFF is also close to the

theoretical curve. The HP video averaging is many dB greater than the theoretical curve

but comes close to the theoretical curve as the frequency increases (after 1 kHz). The

shape of the HP average with pre-amp ON looks similar to the theoretical curve but

12

shifted by 20 dB. The points in the graph close to 60 are only about 4 dB above the noise

level of the receiver.

Tables 2.7 and 2.8 contain the peak and average values measured at 120 kHz

bandwidth. From these are plotted the peak-to-average ratio to compare with theoretically

calculated peak- to-average values. It is clear from the table that the peak and the

average of E7401A pre-amp ON are low due to the saturation of the pre-amp.

Table 2.7: Measured peak values at 120 kHz bandwidth

ESVP ESVP ESVP HP HP 20 dB range 40 dB range 60 dB range Pre-amp Pre-amp ON (dBfLV) (dBfLV) (dBfLV) OFF (dBfLV) (dBfLV)

."-

61.4 59.9 60.1 60.56 40.8

Table 2.8: Measured average values at 120 kHz bandwidth

Repetition ESVP 20 ESVP40 ESVP60 E7401A E7401A E7401A

Rate dB range dB range dB range Pre-arnp Pre-amp VA

(Hz) (dBfLV) (dBfLV) (dBfLV) OFF ON (dBfLV)

(dBfLV) (dBfLV)

50 -8.9 -11.2 -10.6 3.3 -10.5 2.4

I -6.8 -10.5 -9.3 3.4 10.2 3.7 i

1.9 -4.4 1.4 8.9 -7.3 3.8 4.4 0.2 4.6 12.3 -5.7 3.9

2000 28.1 28.4 27.4 21.8 -1.3 3.8 3000 29 29.9 29.2 22.6 1.8 3.4 4000 35.7 34.1 35.1 27.4 4.1 7 5000 36.3 37.3 36 30.7 5.7 6.8 7000 38 38.2 38 33.8 7.6 13.5 10000 43.3 41.6 42.7 36.8 10.8 23.5 20000 48.4 48.4 48.4 42.5 16.6 32 30000 51.6 51.4 51.3 46.5 I 19.8 42 40000 53.5 53.2 53.3 ~22.5 44.2 50000 55.3 55.6 55.7 52.3 25.5 48.3

13

80,-----------.------------.-----------,,-----------.

70 ······· .. ··············· .. ······~Hh

/I 60 , ,

~ 50 1-................................................... + ............. . . Q

<ll 4 0 ~ ............ -, ....................................... : .... , .................... , ...... , ........ "" ... ,'<:>! ..... ,"'.,~,"": Ol

~ g1 <1l 30 .3 -'" <1l (J)

a. 20

--t--

Esvp 20 dB

Esvp 40 dB

EIISp 60 dB

Hp pre-amp on

Hp pre-amp off i ,

10 ................. -V- Hp Video averaging

Theorotical

... _ .... _.n ............. n ..................... , .... _.~ ...... :.:: .. : ... "-.. , """'."'C::.

~ ,

i OL-----------~----------~----------~--------__ ~ 10

1 10

2 10

3 10

4 10

5

Repititon rate (Hz)

Figure 2.4: Comparison of different averaging techniques (120 kHz)

The graph in Figure 2.4 compares peak-to-average of different averaging

techniques from the receiver and analyzer with the theoretical (refer to Appendix C). The

ESVP readings for 50 Hz are approximately 4 dB above the noise level so they may not

be accurate. From the graph, it looks like the measurements from the ESVP fit the

theoretical curve after 1 kHz_ The E7401A pre-amp OFF is consistently several dB above

the theoretical curve. The E7401A video averaging curve does not have a shape similar to

the theoretical curve but comes close to the theoretical curve at the highest frequency.

The E7401A average with pre-amp ON looks similar to the E4701A pre-amp OFF. Note

14

that while the peak and the average of the E7401A are both low, peak-to-average ratio is

compensated and is close to the theoretical curve. The calculation of the theoretical

peak- to-average ratio is discussed in Chapter V.

2.6 Noise emissions from the ESVP and E7401A

Our measuring instruments were not perfectly quiet. Weak emissions from the

ESVP receiver were measured with the E7401A analyzer, and vice versa. The receiver

radiated in a narrow band from 47.099 to 47.105 MHz and the amplitude was around-5

dBIlV. The analyzer had harmonic emissions at 46.99, 47.205, 47.4 and 47.62 MHz. The

amplitude was around 0 dBIlV.

2.7 Summary

The data examined above suggest that the E7401A analyzer is good but has some

deficiencies. There is pre-amp saturation, and the filters should have a higher order to

give better rejection outside the band. The average measurement of pulses has a problem

when the pre-amp is switched on. The E7401A analyzer has several advantages as listed

in the beginning of this chapter.

15

CHAPTER III

Tex-899-B TEST

The Tex-899-B procedure was proposed by the Texas Department of

Transportation. It was developed to support their network of two-way radios installed in

their trucks. This procedure is listed in Appendix A. Results have been reported by Zhou

[13]. The instruments we used to perform this procedure are the following:

1. Radio communication monitor (Rohde & Schwarz CMS 54),

2. Directional coupler (Synergy Microwave KDK-702),

3.50 ohm load,

4. Antenna with coaxial cable (Larsen NMO 50 whip with Maxrad magnetic mount), and

5. Two way radio (Motorola MaraTrac).

The radio communication monitor is used to generate the FM signal and is also used as a

SINAD meter to measure the SINAD value at the output of the radio.

3.1 TxDOT Dodge trucks 2-5643-G and 2-5649-G

We tested two TxDOT trucks. They were both Dodge 1999-model trucks, and

both had dual fuel systems (gasoline and propane). These trucks had a Motorola

MaraTrac radio installed behind the seat. The microphone, speaker and the control box

were installed near the cigarette lighter. A light bar was installed on the roof of one of the

trucks and on the headache rack of the other.

The radios in the trucks were scanned to find the frequencies (modes)

programmed in them. Eight different modes were found and their respective frequencies

16

were noted down. They are listed in the table below. The frequency 47.18 MHz is a

special frequency since it is the only frequency that is common to every Department of

Transportation office in Texas.

Table 3.1 Mode number and its respective center frequency, TxDOT trucks

Mode Number Frequency (MHz)

1 47.18

2 47.06

3 47.24

4 47.26

5 47.34

6 47.02

7 47.04

8 47.08

An antenna was installed at the center of the roof of each truck. The antennas

were tested at Texas Tech University to determine their VSWRs. A network analyzer was

used for this purpose and was scanned from 30 to 80 MHz. Both antennas were found to

be acceptable.

Both the trucks from TxDOT were tested at the same test site (west of Abemathy)

one after other. The eligibility of the test site was determined by the following

measurements listed in Table 3.2. The receiver sensitivity SGR represents the lower limit

for measurement using the receiver (refer to Figure A.1, Appendix A). The load and

coupler was connected and the amplitude of the FM signal was adjusted to get 12 dB

17

SINAD, This represents the noise level of the receiver for a 12 dB SINAD reading (SGd

(refer to Figure A.2, Appendix A). The load was removed and the antenna was

connected. The amplitude of the input FM signal was adjusted to obtain the amplitude

value corresponding to 12 dB SINAD (SGA). This represents the ambient noise level.

The difference between SGA and SGL gives the ambient noise level relative to internal

noise level. This also compensates for the 20 dB attenuation of the direction coupler on

the input FM signal. The difference is added to the receiver sensitivity to add the effect of

the receiver (SGE). SGE has to be less than -6 dBIlV for a site to pass (refer to Site

Qualification Standards, Appendix A).

Table 3.2 Ambient noise levels

Mode 6 Mode 1 Mode 5

47.02MHz 47.18 MHz 47.34 MHz

SGR -12 dBIlV

Recei ver sensi ti vi ty

SGL 8 dBIlV

12 dB with load

SGA 12.3 dBIlV 12.3 dBIlV 12.3 dBIlV

12 dB with antenna

SGAL=SGA-SGL 4.3 dB 4.3 dB 4.3 dB

SGE= SGAL+ SGR -7.7 dBIlV -7.7 dBIlV -7.7 dBIlV

18

The test site passes if SOE is less than -6 dBIlV. From the above table the site

passes for testing the trucks since it has -7.7 dB 11 V.

After checking the level of ambient noise, measurements were conducted on the

noise produced by the truck, and the results are summarized below

Table 3.3 Summary of Tex-899-B test on the Dodge truck from TxDOT (2-5649-0 )

EVENT Amplitude level for 12 dB SINAD value (dBIlV)

47.02MHz 47.18 MHz 47.34 MHz

Key on (gasoline) 13.2 12.9 15.8

Key on (propane) 13.1 12.7 17.7

Light bar 12.2 11.9 13.7

Wipers 13 15.3 16.7

Fan 12.5 12.5 15.9

Fuel pump 13.2 12.9 12.5

Fan and fuel pump 13.8 13.2 17.9

Turn signals 12.2 11.9 12.3

All systems (gasoline) 16 16 20.1

All systems (propane) 16.2 16 19.5

Referring to Appendix A, we can see that the limit that determines the pass or

failure is 0 dBIlV. We used a directional coupler, which adds 20 dB attenuation, so the

19

limit in Table 3.3 is 20 dBJlV. That is, the system passes if the amplitude level for a 12

dB SINAD is less than 20 dBJlV.

Analyzing the above data it is found that this truck failed the Tex-899B test at

47.34 MHz when all systems were running in gasoline by 0.1 dB. Since the difference is

very small, we can consider that this truck passed the test.

A new type of noise was noticed at 47.34 MHz when the key was switched on.

Usually key-on measurements reveal micro-controller narrowband noise, but this new

noise type was found using our EMI receiver to be broadband (refer to Figure 4.1).

Table 3.4 Summary of Tex-899-B test on the Dodge truck from TxDOT (2-5643-0)

EVENT Amplitude level for 12 dB SINAD value (dBJlV)

47.02 MHz 47.18 MHz 47.34MHz

Key on (gasoline) 14.7 14.3 18.3

Key on (propane) 15 14.7 18.4

Light bar 16 15.6 19.9

Wipers 16.2 15 18

Fan 15 14.8 18.6

Fuel pump 13.9 13.6 15.1

All systems (gasoline) 17.4 18.2 19.6

All systems (propane) 17.4 17.6 19.6

20

Table 3.4 shows the Tex-899-B data for the other TxDOT truck. Analyzing the data

reveals that this truck passed the Tex-899-B test (20 dBJlV limit). The new type of noise

was noticed in this truck also when the key was switched on.

3.2 Texas Tech University Dodge truck

We also perfonned the Tex-899-B test on a 1999 Dodge truck belonging to Texas

Tech University. This had no radio and antenna. We used a Larsen antenna with magnetic

mount and a MaraTrac radio, which was programmed for 60 modes. Table 3.5 lists the

modes that were used for the Tex-899-B testing.

Table 3.5: Mode number and its respective center frequency, TTU trucks

MODE NUMBER FREQUENCY (MHz)

6 47.02

12 47.14

14 47.18

22 47.34

23 47.36

24 47.38

26 47.42

The ambient noise levels were measured to determine the eligibility of the test

site. The test site passes if SGE is less than -6 dBJlV. As noted from the data in the Table

3.6 this site passed the test.

21

Table 3.6: Ambient noise levels

Mode 6 Mode 14 I Mode 22 47.02 MHz 47.18 MHz 47.34 MHz

SGR -12 dBIlV Receiver sensitivity SGL 8 dBIlV 12 dB with load SGA 12 dBIlV 10.7 dBIlV 11.7 dBIlV 12 dB with antenna SGAL=SGA-SGL 4dB 2.7 dB 3.7 dB SGE= SG AL + SGR -8 dBIlV -9.3 dBIlV -8.3 dBIlV

The Tex-899-B results for this truck are tabulated in the Table 3.7. The truck did not have

the light bar or an alternative fuel system~ The key-on test was also repeated at two

different frequencies, 47.38 MHz and 47.42 MHz. As shown in Table 3.8, the micro-

controller noise registered up to 35.3 dBIl V. The measurements were not conducted at

47.18 MHz because of a high ambient noise in that frequency.

Table 3.7: Summary of Tex-899-B test on the Dodge truck from Texas Tech

EVENT Amplitude level for 12 dB SINAD value (dBIlV)

47.02MHz 47.34MHz Key on 16.3 21 Wipers 15.4 22.1 Fan 16.3 21.2 Fuel pump 14.9 14.4 Fan, fuel pump and wipers 17 22.3 Fan, fuel pump, wipers and 18 24 washer Engine idle 18 21.2 Engine idle, and all motors 14.9 -except washer All systems (gasoline) 17.4 21.4

22

Table 3.8: Tex-899-B key-on test for other frequencies

EVENT Amplitude level for 12 dB SINAD value (dBIlV)

47.38 MHz 47.42 MHz

Key on 35.3 24.5

This truck failed the test at 47.34 MHz, which is the last frequency in the TxDOT

range. Here the DC motor noise is heavily contaminated by the micro-controller noise,

while at the lower frequency, where the micro-controller noise is low, we can see that the

noise from the DC motors is below the limit.

3.3 Texas Tech University Chevrolet truck

This was a Chevy '99-model truck. It did not have a radio or an antenna, so we

used the same MaraTrac radio used before and the same Larsen antenna. This truck did

not have any extra electrical components installed after purchase from the manufacturer

(like the light bar or the alternate fuel system).

From Table 3.9, we can see that the location selected for the open area testing of

this truck passed the test since its SGE is less than -6 dBJL V.

23

Table 3.9: Ambient noise levels

Mode 6 Mode 1 Mode 5

47.02 MHz 47.18 MHz 47.34 MHz

SGR -12 dBJLV Receiver sensitivity SGL 8 dBJLV 12 dB with load SGA 10.4 10.74 10.4 12 dB with antenna dBJLV dBJLV dBJLV SGAL=SGA-SGL 2.4 dB 2.4 dB 2.4 dB SGE= SG AL + SGR -9.6 dBJLV -9.6 dBJLV -9.6 dBJLV

The measurements were conducted on the noise from the truck and the results are

tabulated below in Table 3.10. From the table, it is concluded that this truck is extremely

silent and passed the TxDOT test. El means engine idle.

Table 3.10: Summary of Tex-899-B test on the Chevrolet truck from Texas Tech

EVENT Amplitude level for 12 dB SINAD in dBJLV

47.02 MHz 47.18 NIHz 47.34MHz

Key on 11.2 10.8 10.8 HVAC fan 11.6 11.3 11.1 Wipers 11.6 11.8 11.8 Fuel pump 10 9.8 10.8

All above + washer 12 11.9 12 Engine idle 16.3 16.3 16.5

Washer + engine idle 15.4 15.4 15.7 El + all motors but no washer or 13.8 13.7 13.9 WIpers El + all motors but no 16.7 - -

washer All systems 19.2 19.2 -

24

3.4 Texas Tech University Ford truck

This truck is a '9S-model Ford truck. The antenna used before was not suitable, so

we used a different length antenna for testing this truck. The same radio was used for

testing. From Table 3.11, SOE is below -6 dBJ1. V, so the site passes the test and is fit for

testing.

Table 3.11: Ambient noise levels

Mode 6 Mode 1 Mode 5

•

47.02 MHz 47.1S MHz 47.34MHz

SOR (receiver sensitivity) -12 dBJ1.V

SOL (12 dB with load) 7.9 dBJ1.V

SGA (12 dB with antenna) 9.9 dBJ1.V 9.9 dBJ1.V 9.9 dBJ1.V

SGAL=SGA-SOL 2dB 2dB 2dB

SGE= SGAL+ SGR 10 dBJ1.V -10 dBJ1.V 10 dBJ1.V

The measurements were conducted on the truck noise, and results are tabulated in

Table 3.12.

Table 3.12: Summary of Tex-S99-B test on the Ford truck from Texas Tech

EVENT Amplitude level for 12 dB SINAD value (dBJ1.V)

47. 47.1SMHz 47.34MHz

Key on (gasoline) 9.9 10 10.3 Wipers 10.3 10.5 10.5 Fan 12.5 12.4 12.4 Fuel pump 10.6 10.6 10.7 Fan, wipers and fuel pump 13.3 12.S 13.5 Fan, wipers, fuel pump 13.9 13.S 13.S and washer motors Engine idle and all motors 14.6 - -on except washers All systems (gasoline) 15.6 15.6 15.9

25

All the values in the table above are much less than the 20 dB limit so we can

conclude that this truck is extremely quiet.

The next chapter discusses the details of 1551/4 tests on the trucks previously

tested under Tex-899-B. By comparing the test results, the validity of the 1551/4 limits is

assessed.

26

CHAPTER IV

J55114 TEST

The Society of Automotive Engineers proposed the J551/4 test. It was devised to

check for interference on a communication receiver in an automobile. The test procedure

is given in Appendix B. The instruments used by us for this test are listed below:

1. EMI receiver (Rohde & Schwarz ESVP),

2. Antenna with coaxial cable (Larsen NMO 50 whip with Maxrad magnetic mount), and

3. 50.Q load.

Table 4.1 contains the internal noise values of the receiver. These values limit the

sensitivity of the receiver.

Table 4.1: Noise level of EM I receiver at 47.18 MHz

Pre-amp ON Pre-amp OFF

Bandwidth (kHz) 120 10 120 10

Peak (dBIlV) 0.6 -11.5 8.6 -3.6

Average (dBIlV) -12.5 -23.3 -3.6 -15.7

4.1 TxDOT Dodge trucks: 2-5649-0 and 2-5643-0

The site where the open area testing was conducted was first tested for ambient

noise, and its suitability was determined. The antenna was mounted on the vehicle and

the ambient noise levels were noted down. The requirement for the site to be suitable for

measurements of vehicle emissions is that the ambient level should be at least 6 dB less

27

than the limit of the vehicle noise to be measured. For CW noise, the limit when using 10

kHz BW and a peak detector is -3 dBIlV [14]. From Table 4.2, the ambient noise was -

6.4 dBIlV. Since this was not at least 6 dB down from -3 dBIlV, the site was not suitable.

For DC motor noise, the limit when using a 120 kHz bandwidth and a peak detector is 50

dBIlV or 40 dBIlV [14, 15]. From Table 4.2, the ambient noise was 5.4 dBIlV. Since

this was well beyond the 6 dB margin, the site was suitable.

Table 4.2: Ambient noise levels at 47.18 MHz

Pre-amp ON Pre-amp OFF

Bandwidth (kHz) 120 10 120 10

Peak (dB Il V) 5.4 -6.4 9.7 - 2.5

Average (dBIlV) -7.2 -18 -3.5 -14.5

Each noise source was switched on and the peak value at 120 kHz bandwidth was

noted. The summary of the test results is shown in the Table 4.3.

Table 4.3: Summary of J551/4 test on TxDOT truck (2-5649-G)

EVENT Amplitude at Amplitude at 47.02 MHz (dBIlV) 47.34 MHz (dBIlV)

Light bar 43.3 to 47 44 to 46 Fan 10.5 to 11.7 15.7 to 17 El + fan 48 to 54.2 52.7 to 54.8 El + fan + light bar 51.2 to 53.9 52.2 to 53.4 El + light bar 51.3 to 53.9 50.4 to 52.1 Fuel pump 11 to 13.5 10.3 to 12.4 Wipers 31.3 to 35.2 28.9 to 32.4 Wipers + washer 52 to 54.9 49.1 to 54.3 El + wipers 53.4 to 54.3 53.2 to 55.2 El 49.7 to 54.5 52 to 53.9

28

The limit for a single DC motor is 50 dBt.tV [14] and for 2 or more DC motors is

40 dBt.tV [14]. From Table 4.3 the truck fails in the cases where the washers were on.

This is different from the result of the Tex-899-B test (refer to Table 3.3). Engine idle

(El) produces spark ignition noise which often has higher peak noise and for which there

is no limit because of noise blanker effectiveness.

Looking at the narrow-band key-on scan, Figure 4.1 shows the TxDOT range

(47.02 to 47.34 MHz) and beyond. The scan reveals the existence of broadband noise

extending from 47.3 to 47.5 MHz (around 200 kHz). The narrow spikes are interference

from vehicles passing near the test site. The micro-controller broadband noise is

discussed in more detail in Chapter V. The noise has no pre-defined limit, so in Chapter

V the limit is defined and the procedure used for obtaining the limit is explained. The

peak of the micro-controller noise is very high but its average is less. The micro-

controller noise is strongest at 47.37 MHz, which is outside the TxDOT range.

~ e .S! E ID

"'-<D "0

~ C. E <{

-'"

'" <D a.

20

15

10

5

0

I ! l : ! !

··················t····················t················ .. ··i····················t····················t······._.

I I ~ I I ~ ! ! i! I

.................. 1 .................... 1 .................... t ................... l .................... i..-- ....••.•... "1--I I ~ i i i I I I ! ~ ~ I - r ! f ~

··················t··· - ····I-··············-···~····--·-····-·-·····t ... --_········· .. 1······

i i I I .................. 1....... ...... .... ....... ..... ! i i

! i

.... _ .. !_ ....... _ .. __ .. __ . .i. .. _ ... _ ..... __ ...... L .... ____ ... _ .. .

i i I f ! i i f I ! ! i ! ! i

···t····················i···········_········I .. ······· ........ . , , , 1 i j

i i i i

: i I ··T··--··-·-······r·····----········-r---····--····

! I i i ! I i ! f ; .................... 1"............. ...... . .... . ,

-5

I ! i 1 i ~

. ;. ! ---··f··· -_··········· .. 1-········ __ ·· ··················1····················;_.,:-············-······.,1. ············r····-··--···--··r! ! I" I i ~ ! t -10 ~ __ ~ ____ ~ __ ~ ____ ~ ____ L-__ -L ____ ~ __ ~ ____ -L __ ~

46.8 46 9 47 47.1 47.2 47 3 47 4

Frequency in MHz

475 476 477 47 8

Figure 4.1: Narrow-band key-on scan from TxDOT Dodge truck 2-5649-G

29

The truck 2-5643 was tested after testing the previous trucks at the same spot, and

the ambient conditions remained stable (refer to Table 4.4).

Table 4.4: Summary of 1551/4 test on TxDOT truck (2-5643-G)

EVENT Amplitude at Amplitude at

47.02 MHz (dBflV) 47.34 MHz (dBflV)

Light bar 26.1 to 30.1 30 to 34.8

Fan 9.6 to 11.3 19.5

El + fan 55.3 to 57 54.3 to 56.2

El + fan + light bar 55.6 to 59.4 56.1 to 59

El + light bar 53.1 to 58.2 55.1 to 59.2

Fuel pump 6.3 4 to 6

Wipers 22.7 to 29.8 29.8 to 34.2

Wipers + washer 55.9 to 60.6 52.8 to 56.2

El + wipers 52.4 to 53.8 53.8 to 54.6

El 52.5 to 56.3 53.2 to 55.6

The limit for a single DC motor is 50 dBflV [14] and for 2 or more DC motors is

40 dBflV [14]. From Table 4.4, the truck fails in the cases where the washer was ON.

From Table 3.4, we can see that this result does not agree with the Tex-899-B test, where

the truck just passed. This creates a requirement for a new limit on DC motors.

Let's look at the narrow-band scan. Figure 4.2 shows a result similar to Figure

4.1. The spike is interference from a vehicle passing near the test site. It was found that

the micro-controller level was about 5 dB lower than that of the previous truck. In this

30

truck, the micro-controller noise starts at 47.34 MHz frequency which is the highest

frequency used by TxDOT.

10

-~ e 0 ,

·············i .. ··· E 5 co ~

E 0

<I: ~ <Il Q)

a.

-5 . :--1----··· -10L-__ -L ____ ~ __ ~ ____ ~ __ _L ____ L_ __ _L ____ ~ __ ~ __ ~

46.8 46.9 47 47.1 47.2 47.3 47.4 47.5 47.6 47.7 47.8

Frequency in M Hz

Figure 4.2: Narrow-band key-on scan from TxDOT Dodge truck 2-5643-0

This micro-controller noise can originate from any of the micro-controllers in the

truck. There were five micro-controllers in the trucks we tested ('99 Dodge). The micro-

controller noise was also recorded on a portable oscilloscope, and this is described in

ChapterV.

31

4.2 Texas Tech University Dodge truck

As described in Chapter rn, a 1999 Dodge truck was obtained from Texas Tech

and a Larsen antenna was mounted on it. The ESVP receiver was used for broadband and

narrow-band measurements as just described for the TxDOT Dodge trucks. The

measurements were conducted at 47.18 MHz, and the results are tabulated below in

Tables 4.5 and 4.6.

Table 4.5: Ambient noise levels (Pre-amp ON)

Bandwidth (kHz) 120 10

Peak (dBJlV) 9.6 to 11.2 -6

Average (dBJlV) -5 -16.5

Table 4.6: Summary of 155114 test on Dodge truck from Texas Tech

I EVENT PEAK (dD .'\ '\ AVERAGE (dBJlV)

Fan 12.8 -2.3

Fuel pump 10.3 -6

Wipers 33 -2.47

All the above 31 to 37 -2.3

All above + washer 53.5 -2.2

Engine idle and all motors on 51.2 -3.9

except the washer

All systems on 52.5 -2.1

32

Analyzing the above, results we conclude that the truck failed in the case of the

washer when we consider the 40 dB/LV [14] suggested limit. From Table 3.7, we can see

that this result does not agree with the Tex-899-B test. This creates a requirement for a

new limit on DC motors.

Looking at the narrow-band scan, the graph in Figure 4.3 shows a key-on scan

that also reveals the existence of the broadband micro-controller noise in this truck as

seen in the trucks before. Since the ambient level (refer to Table 4.5) for the 10 kHz

bandwidth was not 6 dB below the limit, we were not able to determine the result for

narrow-band or CW emission. The micro-controller noise is discussed in the next

Chapter and its limits are found, and the truck was failed because of micro-controller

noise at the highest frequency, 47.34 MHz. Vehicles driving past the test site

contaminated the band of frequencies from 47.22 to 47.28 MHz.

30.----.-----.----.----.----_.----~--_,----_.----~--~

25

g 20 ~ u 'E ID 15 ::e..

o ··················t ....

i ~ ~ ! ·5~--~----~----~--~----~----~--~----~----~--~ 46.8 46.9 47 47.1 47.2 47.3 47.4 47.5 47.6 47.7 47.8

Frequency in M Hz

Figure 4.3: Key-on noise from Texas Tech Dodge truck

33

4.3 Texas Tech University Chevrolet truck

The same Chevy truck discussed in Chapter 3 was borrowed from Texas Tech and

a Larsen antenna with magnetic mount was mounted, and the truck was tested. The truck

was tested at 47.18 MHz at 120 kHz bandwidth

The results are tabulated in Tables 4.7 and 4.8. From Table 4.8, we can see that

the average value of the DC motors changes when the engine is switched on. This truck

fails if we consider the DC-motor peak limit [14] of 40 dBIl V when we look at all motors

running because of the washer. From Table 3.10, we can see that this result does not

agree with the Tex-899-B test. This creates a requirement for a new limit on DC motors.

Table 4.7: Ambient noise levels

Pre-amp ON Bandwidth (kHz) 120 10

Peak (dB Jl V) 5.2 -7.4 Average (dBJlV) -9 -19.8

Table 4.8: Summary of J551/4 test for Chevrolet truck from Texas Tech

Noise Source Peak amplitude A verage amplitude (dBJlV) (dBJlV)

HVACfan 24.7 -8.7 Fuel pump 16.3 -8.5 Wipers 8.1 -8.1 All above 25 -7 Wipers and washer 49 1.9 All above 54 1.5

Engine idle 61.8 -0.9

Engine idle and all 62.2 -4.7 motors on except the washer All above 65.8 3

34

The narrow-band key-on scan along with the ambient is shown in Figure 4.4. The

strange looking high peaks are due to vehicles passing near the test site. From the graph,

we can conclude that there is no broadband micro-controller noise as we saw in the

Dodge trucks.

25.----,----~----.---_.----~----._~_.----_,----._--_.

20

-51-·· .. ············ .. ···q)I~·'11IIr···-

46.9 47

Ambient Key-On Limit

47.1 47.2 47.3 47.4 Frequency (MHz)-->

Figure 4.4: Key-on and ambient noise on the Chevy truck

47.5 47.6 47.7 47.8

The -3 dB~V limit [14] is also plotted in the graph and shows that except for the

frequencies with high peaks, due to vehicles passing near the test site, all others are less

than the limit, so this truck passes the narrow-band noise test.

4.4 Texas Tech University Ford truck

As mentioned in Chapter rn, the Texas Tech Ford truck required a different

antenna to adjust the center frequency to around 47 MHz. The testing was done at the

35

same spot as before. The ambient was quiet at first (refer to Table 4.9), but it got worse

due to lightning so the narrow band scan was abandoned. The broadband test was

conducted at 47.02 MHz at 120 kRz bandwidth, and the results are shown in Table 4.10.

This truck passed the test considering the limit [14] for DC motors. The ignition system

produced less noise compared to the washer motors. The truck was extremely quiet.

Table 4.9: Ambient noise levels

Pre-amp ON

Bandwidth (kRz) 120 10

Peak (dBflV) 14.8 -8.1

Average (dB/lV) -7.8 to -10.8 -19.8

Table 4.10: Summary of J55114 test on Ford truck from Texas Tech

EVENT PEAK (dB/lV) AVERAGE (dB/lV)

Fan 32.7 to 35.7 -2.2

Fuel pump 20 to 22 -7.4

Wipers 29.8 -7.9

All of the above 41.9 -2.9

Wipers + washer 42.7 to 45 0.5

All above 39.6 -1.5

Engine idle 33.2 -7

Engine idle and al1 40 0.3

motors on except the washer

All above 38.2 -4.3

36

In the next chapter, we shall discuss the average measurements, micro-controller

noise and new limits for DC motors and broadband micro-controller noise. The analysis

of average data tabulated in Tables 4.6, 4.8, and 4.10 are discussed in Chapter V.

37

CHAPTER V

A VERAGE MEASUREMENTS

The measurements discussed in the previous chapter involve a peak detector.

There are several other detectors that can be used and that have their advantages over

peak detectors depending on the characteristics of the signal detected. Quasi-peak

detectors can be used to separate two signals that have almost equal peaks but different

duty cycle. Average detectors are used to separate narrow-band signals from broadband

signals.

The problem that led us to the consideration of detectors other than peak was how

to detect DC motor noise in the presence of ignition noise. The average detector seemed

like a good candidate because it gives a low output for low repetition rate pulses like

ignition noise. Figure 5.1 l1lustrates a test conducted in the laboratory, which shows a

comparison of detectors as a function of repetition rate [16].

°1tt0~~t0ttttjjtt~~~~~ Output -10 amplitude r-elativeto input pulse -20 magnitude (dB) -30

-40

·50

1Hz 10Hz 100Hz 1KHz 10KHz Pulse Repetition Rate

Figure 5.1: Comparison of various detectors used for EMI measurements

38

There are several advantages of average detectors:

l.The noise floor (both receiver and ambient) is very low compared to that of peak (refer

to Table 4.1 and Table 4.2).

2. In open area testing, an average detector is more immune to the noise from other

vehicles.

3. The variations in average are less than the variations in the peak. This leads to a stable

limit.

A comparison was conducted in our laboratory to test the different detectors and

their effectiveness in separating the DC motor noise and ignition noise. The experiment

was set up such that the ignition noise was simulated with a pulse generator with a

constant peak amplitude of 55 dBJ.tV. A DC HVAC fan was adjusted in steps and the

peak, quasi-peak and average values were noted. The combined noise was also measured.

The figure below plots the fan noise and the fan-plus-ignition noise. We can see that the

quasi-peak of the total noise does not follow the quasi-peak of the fan, but the average of

the total noise more or less follows the fan average. This proves that the average detector

can be used to estimate the fan noise in the presence of ignition noise.

39

20 50

45 i 1:::= 1

'0 40 .~ .. --

;!::: 0 35

0 > > !Cl 0 .~ ~ 10 30 .2 E E (Q

(Q -0 -0 C 25

£ -"" ID CC Cl

~ L--.«>

1/// .~.-

5 ~20 .-.--re: <D If) > CC

<l:: ::::l

0

~25 ·20 -15 ·'0

15

10

o ·30

/

-25 -20 ·'5

fan peak· ignition peak (dB) fan peak ignition peak (dB)

Figure 5.2: Comparison of different detectors to separate different noise sources

The reasons for choosing the average detector were described above. However,

the average detector turned out to provide other advantages also. These include

measuring broadband micro-controller noise and DC-motor noise without ignition noise

in vehicles. In forthcoming sections we discuss these measurements.

40

·10

5.1 Computation of theoretical peak-ta-average ratio

The theoretical peak-ta-average ratio was used as a reference to compare different

averaging techniques (refer to Appendix C for a sample computer program). The pulse

used for the periodic pulse train was approximated as a trapezoidal function. The width of

the pulse at the half-peak amplitude was considered to be IOns. A fifth-order

Butterworth bandpass filter was chosen, with a version having a 6 dB bandwidth of 120

kHz shown in the sample program. This filter was designed to match closely the shape of

the ESVP receiver fi1ter used in the measurements. The input pulse train's Fourier

transform, consisting of a peliodic series of spectral lines, was multiplied by the gain of

the filter at each spectral line frequency. The spectral lines used spanned a frequency

range of about +/- 6 times the bandwidth of the filter, centered at the filter's mid­

frequency point.

The complex coefficients of the filter output spectral lines are phasors. These

were then each put back into the time domain as a cosine function whose amplitude and

phase came from the phasor value and whose frequency was that of the particular spectral

line. When the results from all the spectral lines were added, the output pulse for a

particular time sample was obtained. In the same way, the outputs of all other time

samples (500 samples) were calculated to produce the total output pulse as a function of

time over one period or fraction of a period, depending on the resolution desired. While

calculating the output, full-wave rectification was performed (as in the ESVP), i.e., the

negative coefficients were converted to positive values and stored. The maximum value

among the 500 samples was found and stored as the peak value of the pulse.

41

The area under the output pulse was calculated by multiplying the sample values

by their time resolution factor and summing the results. The sum was divided by the

period of the pulse train to give the average of the pulse train. The peak of the pulse was

then divided by the average of the pulse train to give the peak-to-average ratio, which

was then converted to dB. This process was repeated for different rep rates, which

changed the values of the period (and hence the average) of the pulse train. Thus the

theoretical peak-to-average ratio was calculated as a function of pulse repetition rate. For

the narrower bandwidth case (9110 kHz), the filter was changed and the calculations were

repeated. The theoretical average was fairly accurate because it can be seen that the peak­

to-average ratio measured from the ESVP receiver matches the calculated peak-to­

average ratio over a range of repetition rates (Figures 2.3 and 2.4).

5.2 Broadband micro-controller noise

This noise was first observed in the TxDOT Dodge trucks tested with key ON

(refer to Figures 4.1, 4.2 and 4.3). This noise is broadband and extends around 150 to 200

kHz. The figure below shows the micro-controller noise at 47.38 MHz recorded through

a portable oscilloscope connected to the AM output of the EMI receiver. As the figure

illustrates, the noise waveform changes with time. The micro-controller noise is centered

at 47.38 MHz. It was observed only on the Dodge trucks.

42

The- scr!i."en From memory 1 ls

CLOSE

The scre"n from memory :2 is displa

CLOSE

Figure 5.3: Micro-controller noise at different instances

The rnicro-controller noise did not have any pre-defined pass-fail limit for use

with the TxDOT trucks. To investigate further, a special scan was conducted on the

Texas Tech Dodge truck showing the peak and the average of the micro-controller noise

at 10 kHz bandwidth. From Figure 5.4, we can see that the peak is almost constant with

frequency but the average varies. This data together with Tex-899-B data was then used

to determine the limit for the micro-controller noise.

43

20.-------~------~-------.-------.-------.-------.

15 ..... ................................................. . ................................ -............................... -............................. .

~ 1 O-----r---I------'-r - r-! :~~::~~~~I::~-~:~::--:~-]:~:::---l;-~;~::-i ' I i

-S-----r------l----I-----r-----i.:,····················_ ......... . ! ! ! , -1 ................................ j ••.•••••••••• _ •••••••••••••••••••• i .......................... _ ............................................................................. .;. ............................... .

I I i i i -15L-------~------~------~-------L------~------~ 47.34 47.36 47.38 47.4 47.42 47.44 47.46

Frequency in MHz

Figure 5.4: Peak and average plot of the micro-controller noise

Tables 3.7 and 3.8 give Tex-899-B SINAD key-on data at 47.34 MHz, 47.38

MHz, and 47.42 MHz. This data is plotted in Figure 5.5 (after subtracting 20 dB for the

coupler) along with the data at these same frequencies from Figure 5.4. From the graph in

Figure 5.5, it is evident that the SINAD value of the micro-controller noise follows the

average, not the peak, so the limit should be set based on the average value of the micro-

controller noise. At 47.34 MHz the SINAD value lies at 1 dB/-lV, which is very close to

the limit of 0 dB/-lV. At this frequency the average value is about -10 dB/-lV. Thus the

average limit was found to be -10 dBJlV, at 10 kHz bandwidth. This limit could not be

44

verified with other trucks because only Dodge trucks seem to have this strange micro-

controller noise.

1\ I

: ~

52 0 ... . ~ E

C!l :s-

O> -0 :::J ...... a. E «

25

20

15

10

5

0

-5

-10

Peak A-.erage

································r·······························r································r·········· .......... · ....... · ... r .... <--__ --,--S_in_a_d----'

..... · ... · ............. · ..... ··~··:· ..... : ....... · ............. ·-................... ·· ............. t· .............................. . ! ! ! I ! ................................. ~ ................................... ~ ..... ~.~" : ...................... ···f·· , ..... ,-......... -, ............. +~ .......... -, ................... ··f· .... , ................... -, .... .

-------1-----'-:-~-----J------f=------l .... : .............................. . ............................... :;:~~~~ ............................... J .............. ···················f······················ ......... 1 .................................. + ..••.•.••.•..••.•••.•••.•...••..

I ! , : I ······_·························r··················· __ ·· ········,···································t··································t··············· ................ + ............................... .

I I I I : ............................... : ................................. ~ .................... ···············f··································f··············_··················f······················· ........ .

I i i i -15L-------~------~------~------~------~------~ 47.32 47.34 47.36 47.38 47.4 47.42 47.44

Frequency (MHz)----->

Figure 5.5: Comparison of peak and average noise amplitude with 12-dB SINAD signal amplitude

5.3 Average limit for DC-motor noise

DC motor noise requires different peak limits depending on the number of

motors [14]. Furthermore the limits do not suit the testing of DC motors when windshield

washer motors are involved. In the hope of finding a single limit we investigated average

measurements. As described before, the possibility of measuring DC motor noise in the

45

presence of ignition noise also seemed to be a good reason to explore the use of average

measurements.

We conducted a laboratory test where the DC motor noise was added to an FM

signal and was connected to the radio. The SINAD meter was connected to the output of

the radio. The values of peak and average of the DC motor noise were recorded for a 12

dB SINAD value.

Table 5.1: Peak and average for DC motors for 12 dB SINAD using ESVP receiver

Fan Fuel pump Fan + Fuel pump

Bandwidth Peak Average Peak Average Peak Average

dBJlV dBJlV dBJlV dBJlV dBJlV dBJlV

120 kHz 49 to 2.9 to 44.6 to 2.7 to 49.6 to 2.9 to

53.5 3.7 49.2 3.6 54.8 4.1

10kHz 27.7 to -2.8 to 26.6 to -2.6 to 27.7 to -2.8 to

31.3 -3.8 29.1 -4.4 32.7 -3.7

From Table 5.1, we can conclude that the average limi t should be 3 dB Jl V at 120

kHz bandwidth. (The average limit is about -3 dBIlV at 10 kHz bandwidth.) This has

been tested in vehicles before (refer to Tables 3.7,3.10,3.12,4.6,4.8 and 4.10) and is

found to be fairly accurate. In all those tables, the events concerned with washer motors

did not fit in the peak limit. The average limit of 3 dBIl V seemed to be better correlated

than the peak. The washer in the Chevy truck produced a lot of noise. We can see that the

average limit was good even in this case. So it was found that a single limit could be set

for the DC motors. This new limit plus the one for micro-controller noise lead to an

46

auxiliary testing procedure that could be coupled with the 155114 test to produce a more

effective procedure for testing the vehic1es. This is described in the following section.

Table 5.2: Peak and average for DC motors for 12 dB SINAD using HP analyzer

_._ ....

! Fan I Fuel pump Fan + Fuel pump

Bandwidth Peak Average Peak Average Peak Average

dBltV dBltV dBltV dBltV dB itV dBltV

120 kHz 43 to .54 to 48 to 51 -2 to 53 to 55 -0.4 to-l

48.5 0.7 -3.2

10kHz 23 to 26 -1.1 to 28 to 32 -5 to 31 to 35 to -5

-1.6 -6.3

Table 5.2 shows the same measurements recorded using the HP analyzer. The

limits do not match those of the ESVP, but this is expected because we saw a difference

in Figure 2.3 and Figure 2.4.

5.4 Comprehensive test procedure

The following procedure describes the 155114 test along with the auxiliary testing

procedure:

1. The first step is to test for the key-on noise. A narrow-band peak scan, which is the

same as the J551/4 test, is conducted. It is followed by a narrow-band average scan.

The peak limit for narrow-band (or CW) micro-controller noise is -3 dBIlV [14], so

check this limit outside the broadband micro-controller noise. (Usually the broadband

noise is a band of frequencies that has very high amplitude mostly above 5 dBltV

peak). Check for the average limit of -10 dBltV in the band of frequencies that has the

broadband noise noted from the peak scan.

47

2. The next step is to determine the noise from DC motors. Turn the motors on one at a

time and measure the peak and average at a 120 kHz bandwidth. Check for a limit of

3 dBIl V in the average value and determine the pass or fail based on the average

limit.

3. Turn all motors on at the same time and measure the peak and the average at a 120

kHz bandwidth. Check for a limit of 3 dBIlV in the average value and determine the

pass or fail based on the average limit.

4. Turn everything on in the vehicle including engine and all DC motors. Do a 120

kHz average scan. Look for spots from step 1 where the micro-controller noise is the

least and check for a 3 dBIlV average limit. Compare it with the value from the

previous step. This gives an estimate of the DC motor noise when the engine is

running, which might be different than when the engine is switched off (refer to Table

4.8).

5. Turn on the engine only, and note down the peak value. There is no limit on ignition

noise [14] because of the effectiveness of the noise blanker in the TxDOT radios.

This measurement is done to get a complete set of data on a truck.

The procedure described here has both J55114 and its modifications that make it

more effective for DC-motor noise and more complete by including broadband micro­

controller noise.

48

CHAPTER VI

CONCLUSIONS

The requirement of synchronizing the limits of two testing standards led to several

results along the course of the research. Assuming Tex-899-B as the reference standard,

efforts were made to modify the limits of the J551 test to make it more comparable to the

Tex-899-B test. Different makes of trucks were tested to help us arrive at several

conclusions. We encountered a new kind of micro-controller noise, which was broadband

in nature.

The Dodge trucks had micro-controller noise generated when the key was turned

on. This noise is broadband and extends to a couple of hundred kHz. There was no pre­

defined limit on this kind of noise. The average limit was determined by us to be -10

dBf.-lVat 10 kHz bandwidth to give a comparable result to Tex-899-B. In the Dodges, it

contaminated all other noise sources in its band of frequencies.

The Chevy truck had a noisy windshield washer, which proved that the peak limit

previously set on DC motors is not suitable for small motors like the washer. It was found

that the average detector gave a good stable limit, which gave a comparable result to that

of the Tex-899-B test. It was determined in our laboratory tests that the limit of the DC

motors should be set at 3 dBllV at 120 kHz BW irrespective of single motor or multiple

motors. This was verified in the truck testing (refer to Tables 3.7, 3.10, 3.12, 4.6, 4.8 and

4.10).

49

Testing with the engine running and with all motors except washer ON showed

that the average noise measured corresponded to the average of DC motors (refer to

Tables 4.6, 4.8 and 4.10). Thus an average measurement can be used to detect the DC

motor noise in the presence of the ignition noise.

Comparing the results from the three Texas Tech University trucks, we find that

there seems to be a correlation between the average detector value and the 12 dB SINAD

value. Figure 6.1 compares the different trucks for the Tex-899-B test and J 55114 test for

the case of all motors except the washer ON. We can see that the average curve is similar

to the Tex-899-B curve whereas the peak curve is not. The Tex-899-B curve is not only

similar to the average curve but also overlaps the average curve.

50

40 .-I. - .------'0 ~ > 30 0 . .---... . ~

-+-Tex899B E 20 --m

~Average "C -Cl) 10 --Peak "C ::J

== 0 a. E ~ ~ et -10

-20 Chevy Dodge Ford

Figure 6.1: Comparison of peak, average and SINAD values of different trucks

50

The modified J55114 test discussed in Chapter V includes the usage of average

detectors along with peak detectors to form a more effective method of testing. The

addition of average limits to the existing J551/4 test brings the results of both tests in

closer agreement.

6.1 Future research

In the future the application of average measurements for EMI measurements should

be considered more seriously. From Table 4.8, the average values of the motors changes

when the engine is switched on, so the possibility of measurement of noise in the

presence of other noise sources should be studied carefully. It would be better to separate

the noise sources when everything is running in the vehicle. The noises could be

separated as ignition, DC motors, micro-controllers and narrow-band noises. Modeling of

the micro-controller noise could lead to better understanding and would allow us to

develop better noise suppression techniques.

51

REFERENCES

1. NAVAIR AD 1115, "Electromagnetic Compatibility Design Guide for Avionics and Related Ground Support Equipment," 3rd Ed., Department of the Navy, June, 1988.

2. White, Donald, R.J., A Handbook on Shielding Design Methodology and Procedures, Interference Control Technologies, Gainesville, VA, 1986.

3. T.L. Clark; M.B. McCollum; D.H.Trout, and K. Javor, "Marsh all Space Flight Center Electromagnetic Compatibility Design and Interference Control (MEDIC) Handbook," Huntsville, Alabama, June, 1995.

4. FCC regulations title 47 telecommunication, chapter I, part 15 - radio frequency devices -- Table of Contents, Subpart C--Intentional Radiators, pages 634-705.

5. "SAE Surface Vehicle Electromagnetic Compatibility (EMC) Standards Manual," Society of Automotive Engineers, HS-3600, Warrendale, PA, 1997.

6. CISPR 25, "Limits and methods of measurement of radio disturbance characteristics for the protection ofreceivers used on board vehicles," International Electrotechnical Commission, Geneva, Switzerland, 1995.

7. American Radio Relay League (ARRL) Inc., "Automotive Interference Solution," Newington, CT - www.arrl.org/tislinfo/rfiauto.html, 1999.

8. Skomal, Edward N, "Man-Made Radio Noise," Chapter 2, Van Nostrand Reinhold, New York, NY, 1978.

9. Service Manual for Test Receiver ESVP, Rohde & Schwarz, Munich, Gennany, 1985.

10. Getting Started Guide for E4700-series EMC Analyzers, Hewlett-Packard, Santa Rosa, CA, 1998.

11. Measurement Guide for E4700-series EMC Analyzers, Hewlett-Packard, Santa Rosa, CA,1998.

12. CISPR 16-1, "Specification for radio disturbance and immunity measuring apparatus and methods, Part 1: Radio disturbance and immunity measuring apparatus," International Electrotechnical Commission, Geneva, Switzerland, 1993.

13. Zhou, Qianlin, "Testing Motor Vehicle for Radio Interference," Master's Thesis, Electrical Engineering Department, Texas Tech University, Lubbock, TX, 1998.

52

14. Trost, Thomas; Ye Jin; Jonsin Yun and Qianlin Zhou, "Testing for FM-Radio Interference in Motor Vehicles," IEEE International Symposium on Electromagnetic Compatibility, 2000.

15. Jin,Ye, "Laboratory Simulation of Motor Vehicle Radio Interference," Master's Thesis, Electrical Engineering Department, Texas Tech University, Lubbock, TX, 1998.

16. Mawdsley, David, "EMC Conducted Emissions measurement," Technical Notes, Laplace Instruments, Norfolk, UK, 1998.

53

APPENDIX A

TxDOT Tex-899-B TEST

RADIO FREQUENCY INTEFERENCE (RFI) TESTING

This test method assures the compatibility of Texas Department of Transportation (TxDOT) fleet vehicles and VHF FM radio equipment operating in the frequency ranges of 30 to 50 MHz and 150 to 174 MHz, but not inclusive. It is intended to identify 90% or more ingress and egress problems.

Definitions

Ingress - any action, reaction, indication, failure to perform or comply, by vehicle equipment and/or accessory items, caused by the activation of the VHF FM radio transmitter in any mode of operation.

Egress - any mode of operation, action, reaction or indication or by the vehicle equipment and/or accessory equipment which degrades the VHF-FM radio receiver effective sensitivity performance by more than six dB.

1. 100 W VHF FM communications transmitter and receiver capable of operating on all TxDOT frequencies. 2. 12 V regulated DC power supply 3. RF FM signal generator with a calibrated attenuator 4. Signal-to-noise audio distortion (SIN AD) meter 5. Receiver audio termination load 6. RF directional coupler rated at 40 dB directional, minimum 7. RF termination load 8. Magnetic-mount antenna for the testing frequencies 9. RF isolation choke, a (6 ft. by 6 ft.) sheet of hardware cloth, laid flat on the test area floor with the coaxial cable making one complete loop approximately four feet in diameter under it 10. RF wattmeter

Facilities

1. Free of high ambient RF noise (receiver test) 2. Equipped with lift capable of raising vehicle tires six inches above floor (transmission test)

54

Safety be must never be compromised during tests. Hazards due to vehicle parts moving and radio frequency/electrical burns exist. Strict compliance with accepted work practices must be observed at all times. Sudden actions may result when the radio transmitter is activated. Stay clear of vehicle and antenna. One person should operate the vehicle, and another the radio.

Egress compatibility

• Receiver qualification

Step Action

1 Assemble a test set-up as shown figure 1.

2 Generate a standard test signal and establish 12 dB SINAD.

_J Kt:l:ord receiver basic sensitivity.

4 Increase signal 6 dB above step 3.

5 Increase peak deviation until SINAD IS degraded to 12 dB SINAD.

6 Record modulation acceptance (Bandwidth).

Compliance of the test setup qualifies the receiver for acceptance testing if:

The receiver basic sensitivity is less than 0.4 IlV (-114 dBm) for 12 dB SINAD The receiver bandwidth shall be a minimum of ± 6.5 kHz and a maximum of± 8.0 kHz.

55

Audio FM signal

RF cable Test radio

RX audio termination generator

cable load

I I DC power SINAD meter

supply

Figure A.l Site Qualification.

• Site Qualification

Step Action

1 Assemble a test set-up as shown in figure 2.

2 Move test vehicle into radio frequency interference shield room or onto site.

3 Temporarily install the magnetic mount antenna on the center of the vehicle loop.

4 Disconnect the battery cable.

5 Terminate the RF line into the RF load terminal.

6 Generate a standard test signal of on-channel center frequency FM modulated with a 1 kHz sine wave tone at ±3.3 kHz deviation.

7 Increase the signal generator RF output level until a 12 dB SINAD indication is achieved.

8 Record sensitivity into RF road termination in dBm.

9 Remove the RF load termination and terminate the RP line into the temporary antenna.

10 Increase signal generator RF output level until a 12 dB SINAD indication is achieved.

11 Record sensitivity into antenna in dBm.

12 Compute the effective sensitivity and determine if the site is qualified.

13 Repeat site qualification at all test radio channels/frequencies to be used.

56

Test antenna I

RP cable

RF termina

load tion

RF isolation cmmler

FM signal generator

Figure - A.2 Test Setup

RF cable Test radio

DC power supply

• Effective Sensitivity Calculation

Step Action

RX audio Audio tennination

cable load

SINAD meter

1 Subtract the sensiti vity into antenna from sensitivity into RP load termination.

2 Record this difference.

3 Subtract this difference from the basic receiver sensiti vity.

4 Record the effective receiver sensitivity in dBm.

5 Convert the effective receiver sensitivity to microvolts.

• Site Qualification Standards

The site is qualified if the effective receiver sensitivity is less than 0.5 JlV (-113 dBm)

57

Egress compatibility

• Egress compliance test for test for test vehicle

Step

1

2

3

4

5

6

7

8

9

10

Action

Reconnect vehicle battery.

Increase the signal generator RF output level until a 12 dB SINAD indication is achieved.

Record the signal generator RF output level.

Activate one vehicle system or accessory.

Increase the signal generator output level until a 12 dB SINAD indication is achieved.

Record the signal generator RF output level.

Repeat Steps 4 through 6 until all vehicle systems and accessories are activated.

Compute total degradation. See NOTE.

Repeat compliance test for all test radio channels/frequencies to be used.

Turn off engine.

NOTE: The electrical system should be designed so the effective sensitivity of the VHF FM receiver requires not more than 1 JlV (-107 dBm) to produce 12 dB or greater SINAD. The effective sensitivity should not exceed 1 JlV for all modes of operation, which should include engine off, engine on, (from idle to full throttle), and all vehicle systems or any combination thereof.

• Test vehicle qualification

The test vehicle passes the egress compliance test when the total degradation does not exceed 6 dB.

58

Ingress compatibility

• Antenna qualification

Step Action

1 Assemble a test set-up as shown in Figure 3.

2 Verify engine is OFF.

3 Raise test vehicle (6 in.) off floor.

4 Verify that magnetic mount antenna IS mounted In center of vehicle roof.

5 Key microphone on test radio.

6 Record nominal forward RF power to the antenna.

7 Record rectified RF power from the antenna.

Adjust length of antenna, if needed, and repeat steps 5 through 7 8 until nominal forward power is 100 watts ± 10 watt and reflected

power is less than 10 % of the forward power.

Vehicle roof

Magnetic-mount

antenna

6.096 m 3.048 m RF (20 ft) (l0 ft)

isolation

RG-58 choke RG-58 coaxial coaxial cable cable

...01 .---- Not less than 10 ft honzontal distance

59

RF Test watt- - radio meter

DC power supply

Figure A.3.Vehicle Qualification for Acceptance

Step Action

1 Start vehicle.

2 Put vehicle in gear and rotate tires at a moderate speed.

3 Activate one vehicle system or accessory. Be certain to check the braking operation.

4 Activate the radio transmitter for approximately five seconds.

Record results as one of the following:

5 l. No adverse reaction 2. Reaction resulting in safety hazard 3. Reaction resulting in a nuisance operation.

6 Repeat steps 3 through 5 until all vehicle systems and accessories are activated.

7 Repeat vehicle qualification for all test radio channels/frequencies to be used.

8 Stop wheels of vehicle and turn off engine. ..

Vehicle Qualification Results

Safety Hazard - No vehicle system and/or accessory shall operate and/or fail to operate as a result of the activation of the VHF FM radio transmitter in a manner which constitutes a safety hazard.

Nuisance operation - correct nuisance operations of any vehicle system and/or accessory.

Failure to meet the criteria of this test method will result in rejection of the vehicle.

60

APPENDIXB

SAE J55114 TEST

Test limit and methods of measurement of radio disturbance characteristics of vehicles and devices, broadband and narrowband, 150 kHz to 1000 MHz

Forward This SAE standard is based on CISPR 25, which has been developed by CISPR Subcommittee D and has been approved to be published. The SAE Electromagnetic Radiation Committee has been an active participant in Subcommittee D and in the development of CISPR 25.

This document provide test limits and procedures for the" protection of vehicle receiver from radio frequency (RF) emission caused by on-board vehicle components."

NOTE - Appendix II provides helpful methodology for resolution of interference problems.

1. Scope ...................................................................................................... .. 2. References ................................................................................................. . 2.1 Applicable Documents .................................................................................. . 2.1.1 SAE Publications .................................................................................... .. 2.1.2 CISPR Publication ................................................................................... . 3. Definition ................................................................................................ .. 4. Requirements Common to Vehicle and Component/Module Emission Measurement. '" ..... . 4.1 General Test Requirements and Test Plan ...................................................... . 4.1.1 Test Plan Notes .................................................................................... . 4.1.2 Determination of Conformance with Limit ..................................................... . 4.1.3 Category of Disturbance Sources (as applied in the test plan) ............................... . 4.1.4 Example of Broadband Disturbance Sources .................................................. . 4.1.5 Narrowband Disturbance Sources ............................................................... . 4.1.6 Operating Conditions ............................................................................. . 4.1.7 Test Report ......................................................................................... . 4.2 Measuring Equipment Requirement.. ..................... '" ................................... . 4.3 Shield Enclosure ................................................................................... . 4.4 Absorber Lined Shielded Enc10sure (ALSE) .................................................. .. 4.4.1 Reflection Characteristic ......................................................................... .. 4.4.2 Objects in ALSE .......................................................... , ........................ . 4.5 Receiver ............................................................................................. .

61

4.5.1 Minimum Scan Time ................................................................................ . 4.5.2 Measuring Instrument Bandwidth .................................................................. . 5. Antenna and Impedance Matching Requirements - Vehicle Test ............................. . 5.1 Type of Antenna ....................................................................................... . 5.2 Measurement System Requirements ............................................................... . 5.2.1 Broadcast Bands ...................................................................................... . 5.2.2 Communication Bands (30 to 1000 MHz) ........................................................ . 6. Method of Measurement ............................................................................ . 7. Limits for Vehicle Radiated Disturbance .......................................................... .

Appendix I Appendix II

Antenna Matching Unit - Vehicle Test. ................................................. . Notes on the Suppression of Interference ................................................ .

Figure 1 Method of Determination of Conformance of Radiated/Conducted Disturbance ........... . Figure2 Example Gain Curve ................................................................................ . Figure3 Vehicle Radiated Emissions- Example for Test Layout (end view with monopole antenna) ..

Table 1 Examples of Broadband Disturbance Sources by Duration ..................................... . Table 3 Measuring Instrument Bandwidth (6 dB) ........................................................ . Table 4 Antenna Types ........................................................................................ . Table 5 Limits of Disturbance - Complete Vehicle ....................................................... .

1. Scope - This SAE Standard contains test limitsl and procedures for the measurement of radio disturbances in the frequency range of 150 kHz to 1000 MHz. The document applies to any electronic/electrical component intended for use in vehicles. Refer to International Telecommunication Union (ITU) Publications for details of frequency allocations. The tests are intended to provide protection for receivers installed in a vehicle from disturbances produced by components/modules in the same vehicle2

.

The receiver types to be protected are: broadcast radio and TV3, land-mobile radio, radio

telephone, amateur and citizens' radio.

The limits in this document are recommended and subject to modification as agreed between the vehicle manufacturer and the component supplier. This document shall also be applied by manufacturers and suppliers of components and equipment, which are to be added and connected to the vehicle harness or to an on-board power connector after delivery of the vehicle.

This document does not include protection of electronic control systems from RF emissions, or from transient or pulse type voltage fluctuations. These subjects are covered in other sections of SAE J551 and in SAE J 1113.

I.only a vehicle can be used to detennine the component compatibility to a vehicle limit. 2 adjacent vehicle can be expected to be protected in most situations. 3 adequate TV protection will result from compliance with the levels at the mobile service frequencies.

62

The Word Administrative Radiocommunications conference (W ARC) lower frequency limit in region 1 was reduced to 148.5 kHz in 1979. For vehicular purposes, test at 150kHz are considered adequate. For the purpose of this document test frequency ranges have been generalized to cover radio services in various parts of the world. Protection of radio reception at adjacent frequencies can be expected in most cases.

2. References

2.1 Applicable Documents the following publications contain provIsIons which, through reference in this text, constitute provisions of this document. At the time of publication, the editions indicated were valid. All documents are subject to revision, and parties to agreements based on this document are encouraged to investigate the possibility of applying the most recent editions of the documents indicated. Members of IEC and ISO maintain registers of currently valid International standards.

2.2.1 SAE Publication Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-000 1: SAE J55111 MAR94 Performance Level and Method of Measurement of Electromagnetic Compatibility of Vehicle and Devices (60 Hz to 18 GHz)

2.1.2 CISPR Publication A vailable from ANSI 11 West 42 Street, NY, NY 10036-8002: CISPR 16-1: 1993-08-Specification for Radio Disturbance and Immunity Measuring Apparatus and Methods. Part 1: Radio disturbance and immunity measuring apparatus

2. Definitions - See SAE J55111.

4. Requirements common to vehicle and component/module emissions measurement

4.1 General Test Requirements and Test Plan

4.1.1 Test Plan Notes A test plan should be established for each item to be tested. The test plan should specified the frequency range to be tested, the emission limits, the disturbance classification [Broad Band (long or short duration) Narrow Band], antenna types and locations, test report requirements, supply voltage, and other relevant parameters.

4.1.2 Determination of Conformation with Limits - If the type of disturbance is unknown, test should be made to determine whether measured emissions are narrow band and/or broad band to apply limits properly as specified in the test plan. Figure 1 outlines the procedure to be followed in determining conformance with limits.

4.1.3 Categories of Disturbance Sources (as applied in the test plan) - Electromagnetic disturbance sources can be divided into three types:4

a. Continuous/long duration broadband and automatically actuated short duration devices b. Manually actuated short duration broad band c. Narrowband

4 For example see 4.1.4 and 4.1.5 and Table 1.

63

MEASURE EUT USING THE AVERAGE

DETECTOR

DETERMINED TO BE NARROWBAND

FAIL

NO

NO

START

MEASURE EUT USING THE PEAK DETECTOR

ARE THE DATA BELOW THE

NARROWBAND LIMIT?

DETERMINE TO BE BROADBAND (REMEASURE WITH QUASIPEAK

DETECTOR, IF REQUIRED BY TEST PLAN

ARE THE BROADBAND DATA BELOW THE BROAD

BAND LIMIT ?

REDESIGN AND RETEST

FIGURE B.I METHOD OF DETERMINATION OF CONFORMANCE OF RADIA TED/CONDUCTED DISTURBANCE

64

YES

4.1.4 Example of Broadband Disturbance sources

Note - The Examples in table 1 are intended as a guide to assist in determining which test limits to use in the test plan.

Table B.l- Example of Broadband Disturbance Sources by Duration.

Continuous

Ignition system Active ride control Fuel injection Instrument regulator Alternator

Long Duration!

Wiper motor Heater blower motor Rear wiper motor Air conditioning compressor Engine cooling

!As defined in the test plan

Short Duration!

Power antenna Washer pump motor Door mirror motor Central door lock Power seat

4.1.5 Narrowband Disturbance Sources - Disturbances from sources employing micro processors, digital logic, oscillators or clock generators, etc., cause narrow band emissions.

4.1.6 Operating Conditions - All continuous and long duration system shall be operated at their maximum RP noise creating conditions. All intermittently operating systems (i.e., thermostatically controlled) that can operate continuously, safely, shall be caused to operate continuously.

When performing the narrow band test , Broadband sources (i.e., ignition system, in particular) may create noise of higher amplitude. In this situation, it will be necessary to test for narrowband noise with ignition switch ON, but the engine not running

4.1.7. Test Report - The report shall contain the information agreed upon by the customer and the supplier

4.2. Measuring Equipment Requirements- All equipment shall be calibrated on a regular basis to assure continued conformance of equipment to required characteristics. The measuring equipment noise floor shall be at least 6 dB less than limit specified in the test plan

4.3 Shielded Enclosure - The ambient electromagnetic noise levels shall be at least 6 dB below the test limits specified in the test plan for each test to be performed. The shielding effectiveness of the shielded enclosure shall be sufficient to assure that the required ambient electromagnetic noise level requirement is met.

The shielded enclosure shall be of sufficient size to ensure that neither the vehiclelEUT nor the test antenna shall be closer than (a) 2 m from the walls or ceiling, and (b) 1 m to the nearest surface of the absorber material used.

4.4. Absorber-Lined Shielded Enclosure (ALSE) - For radiated emISSIOn measurements, however, the reflected energy can cause errors of such as 20 dB. Therefore, it is necessary to apply RP absorber material to the walls and ceiling of a shielded enclosure that is to be used for

65

radiated emission measurements. No absorber material is required for the floor. The following ALSE requirement shall also be met for performing radiated RP emission measurements:

4.4.1 Reflection Characteristics The reflection characteristic of the ALSE shall be such that the maximum error caused by reflected energy from the wall and ceiling is less than 6 dB in the frequency range of 70 to 1000 MHz.

4.4.2 Objects in ALSE In particular, for radiated emission measurements the ALSE shall be cleared of all items not pertinent to the tests. This is required in order to reduce any effect they may have on the measurement. Included are unnecessary equipment. cable racks, storage cabinets, desks, etc. Personnel not actively involved in the test shall be excluded from the ALSE.

4.5 Receiver - Scanning receivers which meet the requirements of CISPR 16 are satisfactory for measurements. Manual or automatic frequency scanning may be used. Spectrum analyzer and scanning receivers are particularly useful for interference measurements. Special consideration shall be given overload linearity, selectivity, and the normal response for pulses. The peak detection made by spectrum analyzer and scanning receiver provides a display indication which is never less than the quasi-peak indication for the same bandwidth. It may be convenient to measure emissions using peak detection because of the faster scan possible than with quasi-peak detection. When quasi peak limits are being used, any peak measurements close to the limit shall be measured using the quasi-peak detector.

4.5.1 Minimum Scan Time - the scan rate of a spectrum analyzer or scanning receiver shall be adjusted for the CISPR frequency band and detection mode used. The minimum sweep time/frequency (Le., most rapid scan rate) is listed in table2:

TABLE B.2 - MINIMUM SCAN TIME

A B

Band 9 to 150 kHz

0.15 to 30 MHz 30 to 1000 MHz

Band definition from CISPR 16 part 1

Peak Detection Does not apply 100 ms/ MHz

1 ms /100 ms / MHz'

Quasi-Peak Detection Does not apply

200 s / MHz 20 s / MHz

lWhen 9 kHz bandwidth is used, the 100 ms / MHz value shall be used

Certain signals (e.g., low repetition rate or intermittent signal) may require slow scan rates or multiple scans to insure that the maxiIl'111m amplitude has been measured.

4.5.2 Measuring Instrument Bandwidth The bandwidth of the measuring instrument shall be chosen such that the noise floor is at least 6 dB lower than the limit curve. The bandwidths in table 3 are recommended.

Note - When the bandwidth of the measuring instrument exceeds the bandwidth of a narrowband signal, the measured signal amplitude will not be affected. The indicated value of impulsive broadband noise will be lower when the measuring instrument bandwidth is reduced.

66

0.15 30

TABLE B.3 - MEASURING INSTRUMENT BANDWIDTH Frequency Band Broadband Broadband Narrowband Narrowband

MHz Peak Peak 30 9 kHz 9 kHz 9kHz

1000 FM broadc ast 120 kHz 120 kHz 120kHz 120 kHz Mobile service 120 kHz 120 kHz 9 kHz 9 kHz

If a spectrum analyzer is used for peak measurements, the video bandwidth shall be at least three times the resolution bandwidth.

For the narrow band/broadband discrimination according to figure!, both bandwidths (with peak and average detectors) shaH be identical.

5. Antenna and Impedance Matching Requirements - Vehicle Test

5.1 Type of Antenna An antenna of the type to be supplied with the vehicle shall be used as the measurement antenna. Its location and attitude are determined according to the production specifications.

If no antenna is to be furnished with the vehicle (as is often the case with a mobile radio system), the antenna types in table 4 shall be used for the test. The antenna type and location shall be included in the test plan.

TABLE BA - ANTENNA TYPES

Broadcast LW AM MW AM SW AM VHF FM

Mobile Services 30 54 70 87

144 -172 420 - 512 800 -1000

5.2 Measurement System Requirements

1 mmonopole 1 m monopole 1 mmonopole 1 mmonopole

loaded quarter wave monopole quarter wave monopole quarter wave monopole quarter wave monopole quarter wave monopole

5.2.1 Broadcasting Bands - For each band, the measurement shall be made with instrumentation which has the specified characteristics. .

5.2.1.1 AM Broadcast

a. Long Wave (150 to 300 kHz)

67

b. Medium Wave (0.53 to 2.0 MHz) c. Short Wave (5.9 to 6.2 MHzi

The measuring system shall have the following characteristics:

a. Output Impedance of Impedance Matching Device: 50 Q resistive. b, Gain: the gain (or attenuation) of the measuring equipment shall be known with an

accuracy of ±0.5 dB. The gain of the equipment shall remain within a 6 dB envelop for each frequency band as shown in figure 2. Calibration shall be performed in accordance with Appendix I.

c. Compression Point: The I dB compression point shall occur at a sine wave voltage level greater than 60 dB(JL V)

d. Measurement System Noise Floor: The noise floor of the combined equipment including measuring instrument, matching amplifier and preamplifier (if used) shall be at least 6 dB lower than the limit level.

e. Dynamic Range: From the noise floor to the 1 dB compression point. f. Input Impedance: the impedance of the measuring system at the input of the matching

network shall be at least 10 times the open circuit impedance of the artificial antenna network in Appendix I.

1

1 Gain (dB)

1

8 ... "" .................. "" ......... " .... "_ ... ",, ................................... _ .......................... " .. , ................................ " .. """"

6 ~--------------------------------------~ flow fhigh

FIGURE B.2 - EXAMPLE GAIN CURVE

6dB envelop

5 Although there are several other short wave broadcast bands, this particular band has been chosen because it is most commonly used in vehic1es. It is expected that other short wave bands will be protected by conformance to the limits in this band.

68

5.2.1.2 FM Broadcast (87 to 108 MHz) Measurements shall be taken with a measuring instrument which has an input impedance of 50 Q. If the standing wave ratio (SWR) is greater than 2: 1, an input matching network shall be used. Appropriate correction shall be made for any attenuation/gain of the matching unit.

5.2.2 Communication Bands (30 to 1000 MHz) - The test procedure assumes a 50 Q measuring instrument and a 50 Q antenna in the frequency range 30 to 1000 MHz. If a measuring instrument and an antenna with differing impedances are used, an appropriate network and correction shall be used.

6. Method of Measurement As a general principle, the disturbance voltage shall be measured at the terminal of the radio receiving antenna placed at the correct vehicle ]ocation(s).

To determine the disturbance characteristics of individual disturbance sources or disturbance systems, all sources shall be forced to operate independently across their range of normal operating conditions (transient effects to be determined)

The disturbance voltage shall be measured at the receiver end of the antenna coaxial cable using the ground contact of the connector as reference. The antenna connector shall be grounded to the housing of the on - board radio (center conductor of the antenna coax is not connected to the on-board radio). The radio housing shall be grounded to the vehicle body using the production harness. The use of a high quality double shielded cable for connection to the measuring receiver is required.

NOTE - The use of ferrite or other suppression material on the coax is recommended, particularly below 2 MHz, for suppression of surface current.

A coaxial bulkhead connector shall be used for connection to the measuring receiver outside the shielded room. See Figure 3.

Some vehicles may allow a receiver to be mounted in several locations (e.g., under the dash, under the seat, etc.). In these cases a test shall be carried out as specified in the test plan for each receiver location.

7. Limit for Vehicle Radiated Disturbances The limits of disturbance may be different for each disturbance source. Long duration disturbance sources such as a heater blower motor must meet a more stringent requirement than short duration disturbance sources. Short duration disturbance may be decided upon by the vehicle manufacturer. For example, door mirror operation may be allowed at a high level of disturbance, as it is operated for only 1 or 2 s at a time. Coherent energy from microprocessors is more objectionable because it resembles desired signal and is continuous.

For acceptable radio reception in a vehicle, the disturbance voltage at the end of the antenna cable shall not exceed the values shown in table 5.

PREPARED BY THE SAE EMR STANDARDS COMMITTEE

69

See 4.3

4

7 10 6

3

8

Antenna Interconnect

I. Measuring instrument 2. ALSE 3. Bulkhead connector 4. Antenna (see 5.1) 5. EUT 6. Typical absorber material 7. Antenna coaxial cable 8. High quality double shielded coaxial cable 9. Housing of on-board radio 10. Impedance matching unit (when required) 11. Optional tee connector with one leg removed

FIGURE B.3. VEHICLE RADIATED EMISSIONS - EXAMPLE FOR TEST LAYOUT (END VIEW WITH MONOPOLE ANTENNA)

70

1

TABLE 5. - LIMITS OF DISTURBANCE - COMPLETE VEHICLE

Terminal Terminal Terminal noise Terminal noise Voltage nOIse Voltage nOIse Terminal

at Receiver Voltage at Receiver Voltage nOIse Antenna at Receiver Antenna at Receiver Voltage

Band Frequency Terminal Antenna Terminal Antenna at Receiver (MHz)

dB(flV) Terminal dB(I!V) Terminal Antenna Broadband dB (I! V) Broadband dB(flV) Terminal Continuous Broadband Short Duration Broadband dB(flV)

QP Continuous QP Short Narrowband P Duration P

P LW 0.15 - 0.3 9 22 15 28 6 MW 0.53 - 2 6 19 15 28 0 SW 5.9 -6.2 6 19 6 19 0

VHF 30 54 6(15 1) 28 15 28 0

VHF 70- 87 6(15 1) 28 15 28 0

VHF 87 108 6(15 1) 28 15 28 6

VHF 144 - 172 6(15 1) 28 15 28 0

UHF 420-512 6(15 1) 28 15 28 0

UHF 800--1000 6(151) 28 15 28 0

All broadband values listed in this table are valid for the bandwidth specified in Table 3.

Stereo signals may be more susceptible to interference than monaural signals in the FM - broadcast band. This phenomenon has been factored into the VHF (87 to 108 MHz) limit.

It is assumed that protection of services operating on frequencies immediately below 30 MHz will most likely be provided if the limits for services above 30 MHz are observed.

lLimit for ignition system only

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APPENDIX I

(Normative)

ANTENNA MATCHING UNIT - VEHICLE TEST

1.1 Antenna Matching Unit Parameters (150 kHz to 6.2 MHz) - The requirements for the measurement equipment are defined in 5.2.1.

1.2. Antenna Matching Unit - calibration - the artificial antenna network of Figure Al is used to represent the antenna including the coaxial cable. The 60 pF capacitor represents the capacitance of the coaxial cable between the car antenna and the input of the radio .

....

son son

SIGNAL GENERATOR

15 pF 11 60 F

ARTIFICIAL ANTENNA NETWORK

............................................................

.. " L. : .... L." " _+-... _ .... _ ..... +. -f''-..... _ ... ... . . . ~ 1"/') .. ~ ....

I I

~ ~

: ........................................................... :

ANTENNA MATCHING

UNIT

MEASlJRING RECEIVER

1.2.1 Gain Measurement - The antenna matching unit shall be measured to determine whether its gain meets the requirements of 5.2.1.1 using the test arrangement shown in Figure A.I

1.2.2 Test Procedure

a. Set the signal generator to the starting carrier frequency with 1000 Hz, 30 % amplitude modulation and 40 dB(JLV)output level.

b. Plot the gain curve for each frequency segment.

1.3 Impedance Measurement - Measurement of the output impedance of the antenna and antenna

72

matching unit shall be made with a vector impedance meter (or equivalent test equipment). The output impedance shall be within a circle on a Smith chart crossing 100 + jO Q, having its center at 50 + jO Q (e.g., SWR less than 2 to O.

APPENDIxn

(Informative)

NOTES ON THE SUPRESSION OF INTERFERENCE

n.l Introduction - Success in providing radio disturbance suppression for a vehicle requires a systematic investigation to identify sources of interference which can be heard in the loudspeaker. This interference may reach the receiver and loudspeaker in various ways:

a. Disturbance coupled to the antenna b. Disturbance coupled to the antenna cable c. Penetration into the receiver enclosure via the power supply cables d. Direct radiation into the receiver (immunity of an automobile radio to radiated

interference) e. Disturbance coupled to all other cables connected to the automobile receiver

Before the start of the investigation, the receiver housing, the antenna base, and each end of the shield of the antenna cable must be correctly grounded.

112 Disturbance Coupled to the Antenna - Most types of disturbances reach the receiver via the antenna. Suppressors can be fitted to the sources of disturbances to reduce these effects.

II.3 Coupling to the Antenna Cable - To minimize coupling, the antenna cable should not be routed parallel to the wiring harness or other electrical cables, and should be placed as remotely as possible from them.

IIA Clock Oscillators - Radiation/conduction from on-board electronic modules may affect other components on the vehicle. Significant harmonics of the execution clock(HE-Clock") must not coincide with duplex transceiver spacings, nor with receiver channel frequencies. The fundamental frequency of oscillator used in automotive modules/components shall not be an integer fraction of the duplex frequency of any mobile transceiver system in operation in the country in which the vehicle will be used

n.s. Other Sources of Information - Corrective measures for penetration by receiver wiring and by direct radiation are covered in other publications. Similarly, tests to evaluate the immunity of a receiver to conducted and direct radiated disturbances are also covered in other pUblications.

73

APPENDIX C

MATLAB PROGRAM FOR CALCULATION OF THEORETICAL PEAK-TO

AVERAGE (Written by Prof. T.F. Krile)

",2

%tau=ha f~width of trapezoidal input se. %tp=period f pulse tra n. 20 ms for the 50 hz se %bw=bandv,Jidth in rad/sec for 6 db point to be at 120 KHz

for the fifth~order But terworth f:i 1 ter. %wo=center frequency of equivalent irst-order ilter.

cutoff and wl lower cutoff an arbitrary itude scal factor.

the time resolution the output se, %which is 500 samples long. %nmax is the number of discrete spectral lines to %be used in f the output se.

() is the Fourier transform of the input pulse,which % is a trapezoidal with a width of 10ns at half %maximum. %gain() is the transfer func of the %coef(j is the spectrum of the output.

is the value of the output pulse. %aver is the average value of the output pulse. %ratio is the peak/average ratio in db. tpi=2*3.14159; tau=10e-9; tp=1/500; bw=tpi*107.5e3; delbw=bw/2;

*47.18e6; wu=wo+delbw; wl=wo-delbw; amp=.6/4; dt=tp/(1*500) ; nmax=round(12*bw/( for n=l:nmax

nn=n-(nmax) 12; w=wo+nn*tpi/tp; pl=w*tau/2;

Itp) )

fil ter.

pre(n)=( Itp)*(amp*tau*sin(pl)/p1)*(sin(p1/2)/(p1/2»; gain(n)=(1/(1+(((w*w-wu*wl)/(w*(wu-wl»)~5)*i»;

coef(n)=gain(n)*pre(n); end c=abs(coef); %plot(c) %This section computes the output pulse. for 1=1:500

ti= (1-250) *dt;

74

end

out=O; for n=l:nmax

nn=n-(nmax)/2; w=wo+nn* ftp; out=out+ahs(coef(n)}*cos( (w-wo)*ti+angle(coef(n)));

end pulse(l)=out; %This subsection full-wave rectifies the if se(1)<O

se(l)= sell); end

\l;This section computes the pk=O;

value of the output.

for n=1:500 if pulse(n»= pk

pk=pulse(n) ; end

end peak=pk %This section computes the average value. ave=O; for n=1:500

ave=ave+pulse(n}*dt; end aver= (ave/tp) ratio=20*loglO(

plot(pulse) aver)

75

Appendix E: Survey of State DOTs

STATE DOT SURVEY SUlVIlVIARY

(COMPILED BY D.J. MEHRL, AUGUST, 2000)

Note: Our first survey mailing was based on a list of lowband users supplied to us by TxDOT and included 23 states. Form this mailing we received 10 responses. A second mailing was based on an Fce list of lowband mobile licenses and included 16 states not in the first mailing. We subsequently received 3 additional responses. The remaining 11 slales were not contacted.

RESPONSE TO SURVEY QUESTION #1: "What percentage of your mobile radios currently operate in the VHF low band? Can you estimate (even roughly) how many low-band mobile radios are currently deployed within your agency?"

State No. of Lowband* No. of Higbband Total % Lowband VHF Radios VHF Radios

Arizona 118 2,387 2,505 5 California 2,434 9,376 11,810 21 Georgia 2,500+ ??? ??? -75 lllinois -2,200 ??? ??? -60 Indiana -2,000 ??? ??? ??? Maine -2,185 115 2,300 95 Mississippi -1,250 ??? ??? ??? Nebraska -2,000 2,000 2,000 100 Ohio 5,247 5,247 5,247 100 Oregon ° 2,100 2,100 ° Texas** 5,350 3,748 9,263 58 Washington -150 ??? ??? ??? West Virginia -2,500 0 2,500 100

Total Lowband 27,934 VHF Radios

* Lowband VHF radio count does not include portable (handheld) radios. It is uncertain as to what extent handhelds might be used inside of vehicles, hence subject to radiated emissions.

** TxDOT data dates back to April, 1998.

RESPONSE TO SURVEY QUESTION #2: 2. TxDOT typically encounters certain makes/models of pickup trucks that present RFI problems. In some cases, wide-band noise problems, appearing on all radio channels, have stemmed from, e.g., electric fuel pumps and HVAC fans. Increasingly, more incidents of microcontroller-related narrow-band noise have cropped up. This noise often requires only the key to be switched on, not the engine running, to be detected. With the engine running

and the vehicle wanning up, the noise may tend to come and go on one, or a few, radio channels.

Can you comment on your experiences (and, if available, your fixes) with RFI problems on various makes/models of vehicles? Are there particular makes/models that present common problems? By compiling a central database of reported problems and fixes from DOT agencies across the nation, we may be able to make identification and remediation ofRFI problems (Please add an extra page ({you need more space.)

Arizona: We experienced problems with 1996/97 ford Taurus' electric fuel pumps that caused RFl problems. Dealer replaced the fuel pumps and the problem was resolved.

California (CALTRANS): We have had many RFI problems in the past. Vehicle equipment tends to interfere with our low band radios. 800 MHz radio equipment tends to interfere with microprocessor controlled electronics. We have initiated many fixes including shielding, grounding and clockfrequency changes.

Georgia: We have encountered problems with Motorola low band radios in certain vehicles. Example: Buick Century Sedans and Wagons, Ford Taurus Sedans and Wagons, and Dodge pickup trucks.

Other comments: Georgia DOT is in the process of converting from tmditionallow band/high band radios to an 800 MHz Southern Link System.

IIlinois: 1999-2000 Dodge Pickups - Fuel Pumps and something else (probably engine control modules on some trucks, not all).

1999-2000 Navistar Trucks Engine control modules on DT 466 engines.

Indiana: A few interference problems from on board computers. No fixes.

Maine: Most of the past problems were with 1994-95-96 Ford and GMC vehicles. We do not have enough newer vehicles to evaluate. Some sources of receiver RFl are Vehicle computers of which this issue was partly resolved with the purchase of special computer filters from Compatibility Products of Round Rock, Texas. Additionally, we have electric fuel pump noise which was eliminated with the use of filters attached very close to the fuel pump. The same source of filters as above were used. Additional sources of noise to receivers were heater blower motors, windshield wiper motors, electronic odometers, Drab and Drak units (alarm systems for heavy duty vehicles such as GMC TOP Kicks) and AM/FM radios.

Standardfilters were used on the blowers and to a less acceptable level on windshield wiper motors. In the AM/FM radio, resonator devices were replaced with crystal filters to eliminate "spike" signals on the radio channels we use. On pickup trucks we mounted the mobile antenna on the extreme rear of the vehicle which did help significantly. It appeared that the GMC pickup trucks, /995-96 were the worst offenders and caused the most problems. Many of which have not been resolved. The cost of computer filters were high, approximately $500 per truck for the computer, fuel and anti-skid brake systems filters.

1t should be noted that Van type vehicles had much less noise generation possibly due to the fact that the antenna was shielded more by the vehicle design. No modifications to the vehicles were required.

2

GlvlC was helpful; however, their engineering staff was not able to really identify the problems or offer any solutions although they seemed to be trying to work 011 fixes that related to more grounding. On the other hand, FORD showed /la interest in resolving the problems.

The SAE stalldard for signal generation by electrollic devices ill vehicles is NOT acceptable due to the rated sellsitivities of receivers in this frequency range. The sensitivity of a modern low band receiver is from 0.2 to 0.3 flV and noise sources are considerably higher from /lumerous sources. The noise blanker function Of! the radios has helped ignition noise but the frequency of other sources is well above its operating range. I agree that manufacturers have not done much about this problem, ill fact they have acknowledged the problem and reduced the sensitivity of the AM portioll of the vehicle radio to reduce noise instead of curing it by proper design and filtering at the source.

Because of the Lack of availablefrequencies in the VHF band, Maine DOT will be on low band for some time to come and needs vehicles which are acceptabLe for use with two-way radios.

Mississippi: 1.) 011 the one-toil ChevroLet trucks we ran into a RFI problem which was caused by the computer. It was causing a problem on 47.24 MHz only. There were no RFI problems on any of the other frequencies. The dealer tried reprogramming the computer, but that did not correct the problem. The computer case in this truck was IIOt grounded to anything. That was the first thing we did. We grounded it to the mefalframe. Next we wrapped all computer connections with a metal fiLm tape. The third thing we did, which was suggested by GM, was to place all ill line filter in the green wire that goes to the battery on this Maratrac radio. This seems to have taken care of the problem. It has been about three months ago and is still working fine.

2.) One-ton 1997 & up Chevrolet dual wheels and dualfuel tanks. See attached from Fleet Operations (ChevroletIGM) on circuit description. We'vefound that adding a 5 pF capacitor across x-I solved it most of the time. With a few we added a IO pF capacitor instead. The problem was intermittent noise on 47.14,47.22, 47.24,47.26 and 47.34 MHz. [Note: Attachments too lengthy to include in this summary.]

Nebraska: GM AM-FM broadcast band radio interferes. Per Delco tech support we changed ceramic resonator to 3.58 MHz quartz crystal.

Other comments: Full size carefully resonated whip helps a lot compared to base load.

Ohio: • Narrow band 98-99 Dodge RAM pickups: air bag circuit. Module replaced by dealer. • Broad band - Ford F-350 wl Power Stroke diesel, 1995 to present. The electronic injector module. The

factory did not support a fix. Note: the F-350 wiring harness is approximately the same length as our standard 114 wave whip. This created a broadly resonant antenna. • Broad band - 1995 GMC pickups w/350 gas engine. Could not determine source of RFJ. Had many discussions with Delco, butfactory did not support a fix. • Broad band - Various Ford pickups wl6 & 8 cylinder gas engines. The factory did not support a fix. • Broad band -1nternational 98-99 466E & 530E engines. RFJ from engine control module. The factory did support a fix. Corrected by installing a filter (bypass capacitor) installed between the engine and floating ground case of the injector module. • Broad band Allison Transmissions. Field replacement of electronic control module. The factory supported thefIX.

Other comments: We located an aftermarket filter from Spectrum Controls. We did not purchase as the cost was $500-600 per unit with a minimum of25 units and installation may have compromised warranty and emissions requirements with Ford.

3

Oregon: We currently do not encounter many RFI problems with new vehicles. Those that we do encounter problems with are required to be corrected by the manufacturer. (We have a 3 dB desense requirement ill our bid specifications. )

Texas: Some recent problems and fixes--Problem: 199711998 Ford F150 Central Timing Module (CTM) narrow-band noise. Fix: New ClM installed by Ford.

Problem: 1997 Ford F J 50 LPG Conversion Processor narrow-band noise and immunity. Fix: New processor by Autotronics.

Problem: 1998 Ford F150 Dual Fuel LPG vehicle HVAC and GFJ processor broadband noise. Fix: NOlle from factory. Ford is contracting with Professional Testing, Inc., to develop a filter.

Problem: 199711998 6.5L GMC diesel vehicle control module (VCM) narrow-band noise. Fix: GM is recalling ten vehicles at a time and replacing the VCM with an enhanced version.

Problem: 1997 Volvo White 1 Cummins engine fuel injector controller broadband noise. Fix: Cummins has a filter to be tested.

Problem: 1997 International Navistar 1 Caterpillar CI0 electronic engine controller broadband noise. Fix: A filter is out to dealerships and ready for installation.

Problem: 1998 Dodge BR 1500 air bag controller narrow-band noise. Fix: Solution being developed by Professional Testing, Inc.

Problem: 1996 GMC Etnyre Asphalt Maintenance Unit on-board computer immunity problem. Fix: None from thefactory. Third letter sent in December, 1998.

Problem: 1999 Chevrolet C7500 series noise was discovered by district before accepting using Acceptance Check Ust.

Washington: Virtually all vehicles with lean bum computers, or computer controlled injection systems produce RFI on some frequency or channel in lqw band between 40-50 MfJz.

Since manylmost older PC units radiated signals in multiples of 4. 7 MHz, the State of Washington made a decision to move the entire fleet to 800 MHz and abandon low band.

West Virginia: Have had low band noise from various vehicles' sub-systems such as fuel pumps, electronic RPM gauges, AM­FM radios and vehicle main microprocessor.

RESPONSE TO SURVEY QUESTION #3: 3. Any other comments you wish to offer? Do you want more information about TxDOT's Tex-JJ60-T or about our modified J551/4?

In response to question #3, all but two survey responses indicated that they would like additional information about TxDOT's Tex-1160-T and our modified J55114 tests.

4